Program

 

 

                                        * Remote

 

Invited Talks

Contributed Talks

Discussions

 

 

MONDAY

 

REGISTRACION 10:00-10:30

 

BREAKFAST 10:30-11:00

 

Theory Session (11:00-12:50, Chair: Lucas Pinol)

 

-  Welcome 11:00h-11:15

- Ana Achúcarro (Leiden University, Leiden, Netherlands). Monday 11:15-12:00.

Title: Opportunities and challenges from multifield inflation

Abstract: TBD.

- Pulkit S. Ghoderao (Imperial College London, London, UK). Monday 12:00-12:15.

Title:Non-Gaussian density perturbations from decay of non-minimally coupled inflaton field

Abstract: We consider a simple and observationally viable theory of an inflaton field coupled non-minimally to gravity and decaying to a massless scalar field through parametric resonance. The effect of this decay process on the primordial density perturbations is then investigated. 

Assuming a separate universe picture, the fields inside each spatially separated comoving Hubble patch enter radiation domination with different curvature depending on the initial scalar field value of that patch. To capture this highly non-linear dependence, a non-perturbative delta N formalism is required. The non-minimal coupling forces mean scalar field values to lie very close to zero through a calculation of Cosmic Variance using first order Cosmological perturbation theory. Symmetry of the potential around zero further makes leading term in non-perturbative delta N expansion negligible. We proceed to derive sub-leading terms and use them to calculate the non-Gaussianity parameter fNL. From parallel numerical simulations with a large number of initial field values, we are able to predict the exact fNL distribution. We expect it to be significant and be observable in cosmological experiments. We also study how fNL changes with different values of non-minimal coupling as well as with coupling strength between the inflaton and scalar field.

- Sebastian Cespedes (IFT, Madrid, Spain). Monday 12:15-12:30.

Title: The hand-made tail: non-perturbative tails from multifield inflation

Abstract: It is becoming increasingly clear that large but rare fluctuations of the primordial curvature field, controlled by the tail of its probability distribution, could have dramatic effects on the current structure of the universe — e.g. via primordial black-holes. However, the use of standard perturbation theory to study the evolution of fluctuations during inflation fails in providing a reliable description of how non-linear interactions induce non-Gaussian tails. In this work, we use the stochastic inflation formalism to study the non- perturbative effects from multi-field fluctuations on the statistical properties of the primor- dial curvature field. Starting from the effective action describing multi-field fluctuations, we compute the joint probability density function and show that enhanced non-Gaussian tails are a generic feature of slow-roll inflation with additional degrees of freedom.

- Rajeev Kumar Jain (Dept. of Physics - IISc, India). Monday 12:30-12:45.

Title: Primordial non-Gaussian correlations of inflationary perturbations with gauge fields

Abstract: We study the primordial non-Gaussian cross-correlations of inflationary scalar and tensor perturbations with gauge fields during inflation. Using semi-classical methods, we derive novel consistency relations for the three-point cross-correlations which exhibit complete agreement with the full in-in results.

- Mattia Cielo (University of Naples, Naples, Italy). Monday 12:45-12:50.

Title: Impact of Planckian sources on the tensor spectrum and bispectrum

 

LUNCH BREAK 12:50-15:00

 

CMB session I  (15:00-16:45. Chair: Yashar Akrami)

 

- William R. Coulton (Flatiron Institute, New York, USA). Monday 15:00-15:45. (yellow room)

Title: Primordial non-Gaussianity constraints from future CMB experiments

Abstract: Measurements of N-point functions of the cosmic microwave background have provided the most stringent constraints on primordial non-Gaussianity. In this talk I will discuss how upcoming experiments, such as the Simons Observatory and CMB-S4, will both improve upon and expand beyond existing constraints. I will outline some of the key challenges to reaching these gains, such as foreground biases and lensing induced noise, and how they can be mitigated. In the final part of my talk, I will discuss how CMB secondary anisotropies will help enable advances in constraints on primordial non-Gaussianity, in a manner complementary to N-point function measurements of primary anisotropies.

- Anil Kumar Neha (Johns Hopkins University, Maryland, USA) (online) Monday 15:45-16:00.

Title: Primordial Trispectrum from kSZ Tomography

Abstract: The kinetic Sunyaev Zel’dovich (kSZ) effect is a secondary CMB temperature anisotropy that provides a powerful probe of the the radial velocity field of matter distributed across the Universe. This velocity field is reconstructed by combining high resolution CMB measurements with galaxy survey data and it provides an unbiased tracer of matter perturbations in the linear regime. In this paper we show how this measurement can be used to probe primordial non-gaussianity of the local type, particularly focusing on the trispectrum amplitude $\tau_{NL}$, as may arise in a simple two-field inflation model that we provide by way of illustration. Cross-correlating the velocity field derived matter distribution with the biased large scale galaxy density field allows one to measure the scale dependent bias factor with sample variance cancellation. Using this method, we forecast that a configuration corresponding to CMB-S4 and VRO results in a sensitivity of $\sigma_{f_{NL}} \sim 0.39$ and $\sigma_{\tau_{NL}} \sim 0.23$. These forecasts predict an improvement factor of 10 and 90 for $\sigma_{f_{NL}}$ and $\sigma_{\tau_{NL}}$, respectively, over the sensitivity using VRO data alone, without internal sample variance cancellation. Similarly, for a configuration corresponding to DESI and CMB-SO, we forecast a sensitivity of $\sigma_{f_{NL}} \sim 2.3$ and $\sigma_{\tau_{NL}} \sim 12$, with improvement factors of 2 and 3, respectively, over the use of the DESI data-set in isolation. We find that a high galaxy number density and large survey volume are what considerably improve our ability to probe the amplitude of the primordial trispectrum for the multi-field model considered.

- Javier Carrón Duque (University of Rome Tor Vergat, Rome, Italy). Monday 16:00-16:15.

Title: Non-Gaussianities in CMB Polarization by extending the Minkowski Functionals framework

Abstract: Minkowski Functionals are high-order statistics that can be extracted from spherical maps such as the CMB, providing additional information to the information in the angular power spectrum. The expected value of these functionals can be very accurately predicted for Gaussian isotropic maps, which turn them into an excellent tool to look for non-Gaussianities in a model-independent way. They have been widely applied to scalar maps such as CMB temperature and lensing, but they can not be directly applied to spin maps such as CMB polarization. In this talk, I will extend the formalism of Minkowski Functionals to CMB polarization (and generally, to spin fields) in two different ways that keep full information of the spin field. I will briefly introduce the theoretical predictions for the Minkowski Functionals in these extensions and I will present Pynkowski: a Python package that can be used to compute them in scalar and spin maps. This framework and software will soon be extended to include other high-order statistics such as peak statistics, as well as other data inputs such as 3D density maps. Finally, I will present the results of applying this framework to Planck polarization data and explain how present and future CMB data can be used to study non-Gaussianities and disentangle between primordial and foreground-induced. I will also show how Minkowski Functionals can be used to assess the Cosmological Principle (for example, by studying the power asymmetry of the CMB temperature). This talk is based on several ongoing projects developed in collaboration with Domenico Marinucci, Nicola Vittorio, Marina Migliaccio, Alessandro Carones, Giuseppe Puglisi, and Giacomo Galloni.

- Benedict Kalus (KASI, Korea). Monday 16:15-16-30.

Title: What will we have learnt about inflation by 2030 if we do not detect f_NL or r?

Abstract: The ability to test and constrain theories of cosmic inflation will advance substantially over the next decade. While optimistic Fisher forecasts predict σ(fNL)<1 for local type PNG, this requires a pristine understanding of observational and theoretical systematics. We, therefore, expect a good chance of fNL=0 not to be ruled out. Furthermore, in a significant class of inflationary scenarios, a low primordial stochastic gravitational-wave background (SGWB) amplitude is correlated with a running α of the spectral index of the primordial density perturbations n_s that is larger than found in the simplest models. With this motivation, we forecast the precision with which n_s and α can be constrained by currently envisaged surveys, including CMB (Simons Observatory, CMB-S4 and LiteBird), optical/near infra-red surveys (DESI and SPHEREx), and 21cm intensity mapping (Tianlai and CHIME). We identify optimal combinations of these datasets for constraining the running and show the their utility in testing and confirming inflation in this situation.

- José Luis Bernal. Monday 16:30-16:45.

Title: Primordial non-Gaussianity with Line-intensity mapping

Abstract: Line-intensity mapping (LIM) is a technique that measures the integrated intensity of spectral lines of all sources and can be understood as a tracer of the large-scale matter distribution, while also providing a census of the interstellar and intergalactic medium between cosmic dawn and today. I will discuss the prospect of measuring local-type primordial non-Gaussianity (PNG) using a joint analysis of the 1- and 2-point statistics of intensity maps, as well as in cross-correlation with the CMB through the kinetic Sunyaev-Zel'dovich effect. PNG is known to have an impact on large-scale structure, which introduces a characteristic bias on the 2-point function and also modifies the mass function of collapsed objects. Combining both 1- and 2-point functions (while properly accounting for the covariance between them) will allow us to capture the signature of non-Gaussianity in a more robust manner in future LIM data sets. Furthermore, by considering cross-correlations with the CMB, we can more precisely measure density modes on the largest observable scales, where the signature of PNG are the most prominent.

 

LSS session I (17:15-18:45. Chair: Violeta Gonzalez-Perez)

- Anze Slosar (BNL, Berkeley, USA). Monday 17:15-18:00 (remote, projected at yellow room).

Title: Constraining non-Gaussianity with next-generation surveys

Abstract: I'll discuss prospects for detecting non-Gaussianity though the next-generation surveys with focus on the LSST.  I'll stress the importance of measuring non-Guassianity through multiple tracers, preferentially from different experiments, in particular as a strategy to minimize systematic effects. I'll describe how existing tools for measuring the power spectrum can be adapted to measurements of the bi-spectrum that harnesses the template marginalization technology that has been developed for power spectrum measurement. Finally, I'll also discuss strategies to better understand the value b_phi which is needed to convert constraints and upper limits into meaningful units.

- Alexandre Barreira ( LMU Munich, Munich, Germany). Monday 18:00-18:15.

Title: Can we actually constrain fNL using the scale-dependent bias effect?

Abstract: The scale-dependent bias effect on the galaxy power spectrum is a very promising probe of the local primordial non-Gaussianity (PNG) parameter fNL, but the amplitude of the effect is proportional to the product of fNL and the linear PNG galaxy bias parameter. Our knowledge of this bias parameter is currently very limited, yet nearly all existing fNL constraints and forecasts assume precise knowledge for it. In this talk I will use the BOSS DR12 galaxy power spectrum to illustrate how our uncertain knowledge of galaxy bias currently prevents us from constraining fNL. For example, for a set of equally plausible assumptions about the PNG bias parameter, the error bar on fNL can vary by as much as an order of magnitude using the same BOSS DR12 data. I will also show how marginalizing over this bias parameter with wide priors is not conservative and leads in fact to biased constraints through parameter space projection effects. Independently of galaxy bias assumptions, the scale-dependent bias effect can only be used to detect nonzero fNL by constraining its product with the bias parameter: the exact value and error bar on fNL remain however undetermined and the result cannot be compared with the CMB. I will also comment on why these issues are important for analyses including the multitracer technique and the galaxy bispectrum. This strongly motivates simulation-based research programs aimed at robust theoretical priors for the PNG bias parameters, without which we may never be able to constrain local-fNL using galaxy data.

- Santiago Avila (IFT - UAM - CSIC, Madrid, Spain). Monday 18:15-18:30.

Title: PNG simulations: validating analyses and putting priors on PNG response

Abstract: The LSS scale-dependent bias of density tracers has been claimed to be the most promising avenue to constrain/measure (local) Primordial Non-Gaussianities (PNG), parametrized by ‘fnl’. However, the response of different tracers to PNG (parameterized by ‘p’ or ‘bphi’) is completely degenerated with ‘fnl’, making it difficult to interpret these constraints in terms of inflation. Hence, a new generation of N-Body PNG simulations is needed to better understand the PNG response of different tracers: halo mass bins, ELG, LRG, QSO, HI, etc. Additionally, simulations represent a perfect scenario to validate analysis pipelines and to ensure that we do not get biased cosmological results. First, I will discuss how the usage of Fixed, Paired and Matched-ICs simulations can dramatically reduce the uncertainties (by a factor of 9) on the PNG parameters: either ‘fnl’ when validating the analysis, or ‘p’/’bphi’ when constructing informative priors. Then, I will discuss how the ongoing PNG-UNITsim simulation effort represent a unique opportunity to put informative priors on ‘p’ or ‘bphi’ that will allow us to actually constrain inflationary models with stage-IV LSS experiments such as Euclid, DESI or SKA. On the one hand, the high mass resolution allows us to resolve the tracers of interest well and to simulate them with semi-analytical models of galaxy formation. On the other hand, the Fixed and Matched initial conditions increases the effective volume of the simulations by a factor of ~90, to be able to put constraints/priors suitable for stage-IV experiments.

- Adrián Gutiérrez Adame (IFT - UAM-CSIC, Madrid, Spain). Monday 18:30-18:45.

Title: The UNIT-PNG sims: Constraining the PNG-response parameter.

Abstract: Measuring the level of Primordial Non-Gaussianities (PNGs) would give us some tight constraints on the inflation model landscape. In the next few years, we will have the data from the Stage-IV galaxy surveys, such as DESI, EUCLID, LSST and SKA. These experiments are expected to constrain the fNL parameter to σ (fNL) ∼1. It would be particularly interesting as this could rule out some models of single/multi-field inflation. In this talk, I will focus on the local type of PNGs. I will discuss our efforts in constraining the PNG-response parameter (p), which turns out to be crucial for obtaining an unbiased measurement of fNL. For that objective, we have run one of the most advanced state-of-the-art N-body simulations with local PNGs, the UNIT-PNG Sim, with 4096^3 DM particles which implements the fixed, paired and matched-ICs techniques described in Angulo&Pontzen(2016) and Avila&Adame(2022) Then, I will describe how we are using the clustering of dark matter halos in our simulation for constraining the PNG-response parameter and our preliminary results. Finally, I will talk about our future prospects on populating the DM-only simulation with HODs and SAMs for studying the possible dependence of the PNG-response parameter with the tracer and providing realistic priors to the next-generation galaxy surveys

- Utkarsh Giri (University of Wisconsin-Madison, Wisconsin-Madison, USA). Monday 18:45-19:00.

Title: Robust Neural Network-Enhanced Estimation of Local Primordial Non-Gaussianity

Abstract: When applied to the non-linear matter distribution of the universe, neural networks have been shown to be very statistically sensitive probes of cosmological parameters, such as the linear perturbation amplitude σ8. However, when used as a "black box", neural networks are not robust to baryonic uncertainty. We propose a robust architecture for constraining primordial non-Gaussianity fNL, by training a neural network to locally estimate σ8, and correlating these local estimates with the large-scale density field. We apply our method to N-body simulations, and show that σ(fNL) is 3.5 times better than the constraint obtained from a standard halo-based approach. We show that our method has the same robustness property as large-scale halo bias: baryonic physics can change the normalization of the estimated fNL, but cannot change whether fNL is detected.
 

 

TUESDAY

 

 

BREAKFAST 9:30-10:00

 

LSS session II  (10:00-11:00 & 11:30-12:30, chair: Matteo Martinelli)

- Eva-Maria Mueller (ICG, Portsmouth, UK). Tuesday 10:00-10:45 (yellow room).

Title: Primordial non-Gaussianity from eBOSS DR16

Abstract: I will present results on PNG from the scale dependent halo bias using the eBOSS QSO DR16 dataset.

- Oliver Philcox (Princeton University, Princeton, USA). Tuesday 10:45-11:00.

Title: Constraining Inflation with Galaxy Surveys

Abstract: Over the next decade, galaxy surveys will play a key role in constraining the physics of inflation, primarily through measurements of primordial non-Gaussianity (PNG) amplitudes. In this talk, I will discuss recent progress on bounding both local and non-local PNG from galaxy surveys. These respectively place constraints on multi-field and single-field scenarios, and can be translated into bounds on underlying physical parameters entering the Effective Field Theory of inflation. In particular, I will highlight new measurements from the BOSS galaxy survey, which are the first to (a) include non-local PNG, and (b) make full use of the galaxy bispectrum, via robust perturbative modeling. I will close by commenting on the prospects for measuring PNG from the next generation of surveys, and discuss this will become competitive with the CMB.

COFFEE 11:00-11:30

- Dionysios Karagiannis (UWC Astrophysics, South Africa, Africa). Tuesday 11:30-11:45.

Title: Quasi-maximum likelihood estimation of primordial non-Gaussianity in the non-linear matter field

Abstract:  Future Large Scale Structure surveys are expected to improve over current bounds on primordial non-Gaussianity (PNG), with a significant impact on our understanding of early Universe physics. The level of such improvements will however strongly depend on the extent to which late time non-linearities erase the PNG signal on small scales. In this talk, I will present a simulation-based methodology for the joint estimation of PNG amplitudes (fNL) and standard ΛCDM parameters, combining optimally power spectrum and modal bispectrum measurements. I will discuss how much primordial information remains in the bispectrum of the non-linear matter density field, and how adding the matter power spectrum, which contains negligible information about PNG by itself, helps to significantly improve the constraints. Finally, I will briefly comment the case of the halo density field.

-Antonino Troja (UNIPD-INFN, Padua, Italy). Tuesday 11:45-12:00.

Title: Modeling the Angular Bispectrum in Photometric Galaxy Surveys

Abstract: We measure the angular bispectrum of the matter density fields from numerical simulations and compared the result with the leading-order prediction in Perturbation Theory and the one derived from available fitting functions of the three-dimensional bispectrum. We also compare an estimate of the bispectrum variance based on the simulation results with the simple Gaussian theoretical expectation. This is a first step toward assessing the information content of higher-order angular correlation functions with the specific goal of possible applications to the analysis of photometric redshift surveys. A new code exploiting the power of FFTLog was developed to make faster bispectra models.

-Marco Marinucci (TFD, Israel). Tuesday 12:00-12:15.

Title: Model independent approach to Large Scale Structure

Abstract: I will introduce the role played by symmetries in the perturbative expansion of the large-scale structure. In particular, I will describe how to establish which of the coefficients of the perturbation theory kernels are dictated by symmetries and which not. Up to third order in perturbations, for the dark matter density contrast (and for the dark matter velocity) only three coefficients are not fixed by symmetries and depend on the particular cosmology. For generic biased tracers this number rises to seven in agreement with other bias expansions. A crucial role in this analysis is provided by extended Galilean invariance, which follows from diffeomorphism invariance in the non-relativistic limit. We identify a full hierarchy of extended Galilean invariance constraints, which fix the analytic structure of the perturbation theory kernels as the sums of an increasing number of external momenta vanish. This approach is especially relevant for non-standard models that respect the same symmetries as ΛCDM and where perturbation theory at higher orders has not been exhaustively explored, such as dark energy and modified gravity scenarios. I will describe how to use this approach to perform general model-independent analysis based only on symmetry principles for realistic surveys. To conclude, I will show how to generalize this approach to models with non-Gaussian initial conditions.

-Thomas Flöss (University of Groningen, Netherlands). Tuesday 12:15-12:30.

Title: Primordial non-Gaussianity and non-Gaussian Covariance

Abstract: In the pursuit of primordial non-Gaussianities, we hope to access smaller scales across larger comoving volumes. At late times, the search for primordial non-Gaussianities is hindered by gravitational collapse, which induces secondary non-Gaussianity that swamps the weaker primordial signal. Additionally, it couples modes of different wavelength through (off-diagonal) covariance, reducing the amount of unique information available from the tracer field (e.g. galaxies or 21-cm). We assess the impact of such non-Gaussian covariance on the Fisher information of the primordial non-Gaussian amplitude f_{NL}, with a particular focus on higher redshifts, where this impact has previously been estimated to be negligible. We will comment on possible avenues to circumvent the impact of non-Gaussian covariance when estimating f_{NL} from future surveys.

 

LUNCH BREAK 12:30-14:30

 

Special discussion: Bootstrap & Cosmic Correlators (14:30-15:45 , moderator: Sébastien Renaux-Petel) 

 

Panelists: 

 

- Dong-Gang Wang (University of Cambridge, Cambridge, UK). 14:30-14:45.

Introduction +

Boostless Cosmological Collider Bootstrap

- Sébastien Renaux-Petel (IAP, Paris, France). 14:45-14:50.

Cosmological bootstrap in slow motion and the low speed collider

- Denis Werth (Sorbonne University -IAP, Paris, France). 14:50-14:55 .

Inflationary Correlators Beyond Weak Coupling : a Numerical Approach

- JISHNU SAI PUTHIYEDATH (IISC, India). 14:55-15:00.

On the primordial correlation of gravitons with gauge fields

- Hemza Azri (UAEU, Abu Dhabi). Tuesday 15:00-15:05.

Two-field affine inflation

Discussion by all 15:05-15:45

COFFEE 15:45-16:15

Theory + PBH session  (16:45-18:35, chair: Matteo Fasiello)

- Vincent Vennin (APC, Paris, France). Tuesday 16:15-17:00 (yellow room).  

Title: Non-Gaussianities from primordial quantum diffusion

Abstract: I will show that primordial quantum diffusion unavoidably generates non-Gaussian, exponential tails in the distribution of inflationary perturbations. This type of non-Gaussianity cannot be captured by perturbative parametrisations, and it leaves specific imprints on the statistics of collapsed structures that I will discuss.

 

- Joseph Jackson (University of Portsmouth, Portsmouth,  UK). Tuesday 17:00-17:15 .

Title: Numerical simulations of stochastic inflation using importance sampling

Abstract: Primordial black holes are expected to form from large, but rare, cosmological fluctuations in the tail of the probability distribution arising from inflation. I will present how importance sampling can be used to efficiently investigate the far, numerically expensive, probability tail of these fluctuations, finding non-perturbative deviations from Gaussianity. This is done by solving the first-passage time problem in the Langevin processes to find the distribution of the local duration of inflation in e-folds. By the stochastic-$\delta N$ formalism, these are related to the curvature perturbation at the end of inflation. What previously would take supercomputers weeks, or in principle even years, can be done in hours with just a single CPU using this approach.

- Andrew Gow (ICG-University of Portsmouth, Portsmouth,  UK). Tuesday 17:15-17:30 .

Title: Beyond perturbative non-Gaussianity for primordial black holes

Abstract: Primordial black holes (PBHs) are expected to form from a flat part of the inflaton potential, where stochastic effects must be taken into account. The stochastic formalism allows these effects to be handled in a non-perturbative manner, and predict non-Gaussianity in the PDF of the curvature perturbation. To connect this to PBH formation, a non-perturbative treatment of these non-Gaussianities is required. I will present such a treatment, and discuss the effect on PBH formation for some simple examples.

- Albert Stebbins (Fermilab, Illinois, USA). Tuesday 17:30-17:45 .

Title: Primordial Supermassive Black Holes?

Abstract: This talk will address the conundrum of the existence of the most massive supermassive black holes (SMBH) within a billion years after the big bang. This is not consistent with unadorned $\Lambda$CDM without persistent extreme super-Eddington growth for which there is no other evidence. Production of primordial intermediate mass black holes as seeds for the largest SMBHs requires some adornment of the early universe $\Lambda$CDM scenario. A more extreme hypothesis discussed here is that the largest SMBHs existed in the early universe accreting relatively little additional mass since that time. Evidence for and implications of this hypothesis are discussed including estimates of the mass function and observational signatures in the CMBR. The large non-Gaussian inhomogeneities required for this scenario is discussed.

- Angelo Caravano. Tuesday 17:45-18:00.

Title: Lattice simulations of axion-U(1) inflation

Abstract: If gauge fields are coupled to an axion field during inflation, they can lead to unique observational signatures. However, this system often shows strong backreaction effects, invalidating the standard perturbation theory approach. In this talk, I present the first nonlinear lattice simulation of an axion-U(1) system during inflation. The simulation is used to fully characterize the statistics of primordial scalar fluctuations. We find that non-Gaussianity is large in the linear regime, whereas it is suppressed when the dynamics becomes nonlinear. This relaxes bounds from overproduction of primordial black holes, allowing for a richer phenomenology at large scales.

- Nilanjandev Bhaumik (IICS, Bengaluru, India). Tuesday 18:00-18:05 (5min).

Title: Stochastic gravitational waves background to probe the reheating histories in the presence of primordial black holes

Abstract: Primordial black hole (PBH) is one of the most promising cold dark matter candidates in recent years. The signature of PBHs in the stochastic gravitational-wave background (SGWB) is natural as PBH formation requires a significant amplification in inflationary scalar curvature perturbation, which sources the tensor perturbation in second-order and leads to a detectable amplification in the SGWB. We explore this possibility to probe different possible reheating histories. We find a matter-dominated reheating phase after the inflation to leave significant imprints both on PBH and SGWB. On the other hand, isocurvature perturbation from PBH distributions contributes to the adiabatic perturbation. It leads to detectable amplification in the induced GW background if PBHs dominate the universe for a small duration. Combining these two effects can help us probe ultra-low mass primordial black hole scenarios and details of reheating histories, leaving diverse implications for cosmology and particle physics.

CITY TOUR(OPTIONAL) 19:00-21:15

 

 

BREAKFAST 9:30-10:00

 

LSS (-higher orders) session III (10:00-11:00 & 11:30-12:30,  chair: Ashley J. Ross & Martín de los Ríos)

- Fabian Schmidt (MPA, Garching, Germany). Wednesday 10:00-10:45 (yellow room).

Title: Field-level inference and PNG

Abstract: I will describe a novel, effective-field-theory-based approach that attempts to extract the information in the entire galaxy density field, rather than compressing it into summary statistics, while robustly marginalizing over the complexities of galaxy formation. I will then give a preliminary outlook on what to expect for constraints on primordial non-Gaussianity from this field-level inference.

 

- Hector Gil-Marin (ICCUB, Barcelona,  Spain). Wednesday 10:45-11:00.

Title: The role of the galaxy bispectrum and trispectrum for PNG detections in LSS

Abstract: We explore the role that the galaxy higher-order functionals, the bispectrum (3pt) and trispectrum (4pt) have in the on-going and future galaxy surveys for detecting potential signatures of inflation. Thanks to the developments of new algorithms, we are now able to efficiently measure these functions from synthetic and actual galaxy catalogues, and check their role when constraining the fnl and gnl parameters. In addition, newly developed compression techniques allow us to reduce the data-vectors down to a tractable number of elements without losing a significant amount of information. We present the results of analyzing 5000 realizations of the dark matter Quijote suite in redshift space. Employing the data-vector consisting of the power spectrum, bispectrum and trispectrum signals with the full covariance matrix estimated from the same suite of 5000 simulations, we are able to quantify the added-value provided by the trispectrum when constraining fnl and gnl, in combination with other cosmological parameters. This is the first time both power spectrum, bispectrum and trispectrum has been consistently measured and employed in a LSS catalogue to extract cosmological information. We find that the errors on the fnl parameter are reduced by a factor of 32% compared to those obtained without using the trispectrum. When the quadrupole information is added (both to the bispectrum, and especially to the trispectrum), the gain is boosted by a factor fo 10. These results offer a promising and complementary way to detect PNG from the halo scale dependent bias signal in the power spectrum. Ref. https://arxiv.org/abs/2009.02290, https://arxiv.org/abs/2104.03976.

COFFEE 11:00-11:30

- Julius Wons (UNSW Sydney, Sydney, Australia). Wednesday 11:30-11:45.

Title: Constraining Primordial Non-Gaussanities using the Density and Velocity Field

Abstract: In this talk, I explore the ability to constrain the non-Gaussanities using the matter and velocity power spectrum. The density and velocity field is decomposed into spherical harmonics. Then the KSW estimator, which is used for CMB constraints on fN_L, can be applied to the matter and velocity modes. This allows future LSS surveys to constrain all shapes of non-Gaussanities coming from a separable bispectrum, e.g. local, equilateral, orthogonal. I will provide a prospect of the constraining power of future experiments and what would be required to reach sigma(f_NL)>1.

- Zachery Brown (University of Rochester, Rochester,  USA). Wednesday 11:45-12:00.

Title: PNG sensitivity in galaxy correlations of order n > 2

Abstract: Traditionally, measurements of primordial non-Gaussianity (PNG) are extracted from large-scale structure (LSS) via 2 and 3 point statistics. Advances in clustering algorithms are now employed to measure LSS correlations to higher order (n = 4, 5, etc). Using one such algorithm which estimates the npcf by convolving the matter density field with spherical kernels, we evaluate the npcf of mocks with varying fNL. We observe sensitivity to PNG in higher order statistics at n = 4 and n = 6. We construct toy model data to simulate the expected clustering signal corresponding to a particular value of fNL. From these, we evaluate the sensitivity of our model to fNL and to the PNG bias. By including correlations of order n = 4 and n = 6, we achieve more than twice the sensitivity to PNG than smodels including only correlations of order n = 2.

- Sukhdeep Singh (IIT Kharagpur, India). Wednesday 12:00-12:15 .

Title: Fast Estimator for Bispectrum of 3D Cosmological Fields

Abstract: In the era of precision cosmology, the study of clustering statistics beyond power-spectrum (Fourier transform of 2-point correlation function) is very crucial to capture detailed features of underlying non-Gaussian cosmological fields. Bispectrum (Fourier counterparts of 3-point correlation function), the lowest order statistics sensitive to non-Gaussianity, of density field distribution in real and redshift space provide great deal of cosmological information regarding the physics of the very early Universe, subsequent growth of structures and constraining various model parameters. However, these statistics are very computationally expansive due to their high dimensionality. It is necessary to develop their fast and accurate estimators to analyse the enormous amount of data from ongoing and upcoming future galaxy surveys like LSST, DESI, EUCLID etc. We have developed a Fast Fourier Transform based estimator of binned bispectrum for 3D cosmological density fields by linearly binning the wave-vector space (k-space) in uniform concentric spherical shells. The parameterization of triangles formed by different wave-vectors (Fourier modes) is taken in such a way that the shape and size dependence of bispectrum, corresponding to each possible closed triangle configuration, can be studied separately. The estimator is also implemented to analyse the monopole moment of redshift space bispectrum of field possessing linear redshift-space distortion caused by peculiar velocities of galaxies. The estimator is very fast and results are in good agreement with analytical predictions. This can further be used to analyse survey data to explore the features of cosmic fields and extract precious cosmological information.

- Clement Stahl (ObAS, Strasbourg, France). Wednesday 12:15-12:30.

Title: Primordial Non-gaussianities at galactic scales (TBC)

Abstract: We entertain the idea that large primordial non-gaussianities at Mpc scales could change the galaxy formation process and alleviate some long standing small scale problems of LCDM on these scales.

LUNCH BREAK 12:30-14:45

Discussion: Theory model systematics in PNG from LSS (14:45-15:45 , moderator:  Alexandre Barreira   ) 

Panelists: 

- Alexandre Barreira ( LMU Munich, Munich, Germany).

- Santiago Avila (IFT - UAM - CSIC, Madrid, Spain).

-William R. Coulton (Flatiron Institute, New York, USA).

-Oliver Philcox (Princeton University, Princeton, USA).

COFFEE 15:45-16:15

LSS (-systematics) session IV (16:15-18:00,  chair: Eva-Maria Mueller )

- Ashley J. Ross (Ohio State University, USA). Wednesday 16:15-17:00 (yellow room).

Title: Pathway to measuring robust large-scale structure statistics for primordial non-Gaussianity and beyond

Abstract: Contaminants of large-scale structure maps generically induce false power at the largest scales measurable by a given survey. Controlling this systematic contribution is thus of particular interest for primordial non-Gaussianity measurements. I will review recent progress and present my views of the approach that is most likely to yield robust results while conserving the statistical power to distinguish inflationary models.

 

- Jose Bermejo Climent (University of Rochester, Rochester, USA). Wednesday 17:00-17:15.

Title: Measuring primordial non-Gaussianity from the cross-correlation between DESI Luminous Red Galaxies and Planck CMB lensing

Abstract: The cross-correlation between matter tracers and CMB fields encodes important and unique information. In particular, it has been reported the capability of the CMB lensing - galaxy clustering cross-correlation to constrain the primordial local non-Gaussianity fNL, due to its imprint on the galaxy bias scale dependence. We use the Planck 2018 lensing maps and Luminous Red Galaxies (LRG) from the DESI legacy imaging survey used to select spectroscopic DESI targets. To remove the systematics at large scales which could likely bias a fNL measurement, we apply to the LRG maps a neural network pipeline for imaging systematics mitigation and test its performance with lognormal mocks. We find the LRG - CMB lensing cross-spectra are less sensitive to systematics than the LRG autospectra. At the parameters level, we obtain a fNL uncertainty around ~40-50 from the LRG - Planck lensing cross-correlation and ~10-15 from the LRG autocorrelation, marginalized over the galaxy bias and shot noise. Our results are an independent test on primordial non-Gaussianity and will be improved with the addition of further DESI tracers such as ELG and QSO.

- Steve Cunnington ( University of Manchester,  Manchester , UK). Wednesday 17:15-17:30.

Title: First steps towards probing ultra-large-scales with the SKAO

Abstract: Wide-sky surveys with radio telescopes such as the Square Kilometre Array Observatory (SKAO) have the potential to lead the way in probing the largest scales. This will be achieved by surveying diffuse 21cm emission from extragalactic neutral hydrogen (HI), a technique known as HI intensity mapping. This will be a primary aim for the future SKAO once constructed. However, pathfinder experiments such as the 64-dish MeerKAT telescope are already operational and will provide spectroscopic surveys with competitive volumes. I will present the first detection of cosmological signal using HI intensity mapping with a multi-dish array. This detection was achieved by cross-correlating MeerKAT pilot survey intensity maps with overlapping optical galaxies from the WiggleZ Dark Energy Survey. A measurement of the power spectrum between these fields provided a 7.7σ detection of a cross-correlation. To achieve this detection, the multi-dish array must map the radio emission using the single-dish data from each element of the array, rather than as a conventional interferometer. This detection is the first practical demonstration of the multi-dish auto-correlation intensity mapping technique, crucial for the SKAO's capability to probe ultra-large scales. This marks an important milestone in the roadmap for the cosmology science case with the full SKAO.

- Walter Riquelme (IFT - UAM-CSIC, Madrid, Spain). Wednesday 17:30-17:45.

Title: Primordial non-Gaussianity with the Dark Energy Survey

Abstract: In this talk, I'll summarize the current status and future perspectives on the measurement of Primordial non-Gaussianity within the Dark Energy Survey collaboration. I'll focus on presenting the methodology to measure local fNL from the Dark Energy Survey (DES) data using the 2-point angular correlation function (ACF) via the induced scale-dependent bias. One of the main focuses is on the treatment of integral constraint, a condition that appears when estimating the number density of galaxies from the data itself. This is especially relevant for PNG analyses and key for obtaining unbiased fNL constraints. The methods are analyzed and validated using two types of simulations: GOLIAT N-body simulations with non-Gaussian initial conditions and the Gaussian ICE-COLA mocks that follow the DES-Y3 BAO angular and redshift distribution. Using the ICE-COLA mocks, we forecast constraints in fNL when using the BAO sample. To assess the impact that using different galaxy samples could have when measuring fNL, I'll also briefly mention the current efforts to look for an optimised galaxy sample using DES-Y6 final data.

- Kevin Pardede (SISSA, Trieste, Italy). Wednesday 17:45-18:00.

Title: Bispectrum and finite volume effects: window convolution

Abstract: One particular class of observables to study galaxy clustering are Fourier-space summary statistics of the galaxy distribution. The higher order statistics such as the galaxy bispectrum offers non-trivial information with respect to the power spectrum, and in particular can directly probe a primordial non-Gaussian component, possibly shedding light on the interactions taking place during inflation. Including analysis of higher-order statistics however, comes with extra modelling complexity. In this talk, I will focus on the challenge to properly model the effects of the survey window in the bispectrum. Finite volume effects like this is especially important in order to get an unbiased measurements of parameters sensitive to large-scale information, e.g. $f_{NL}$. In fact, the conventional FKP (Feldman-Kaiser-Peacock)-like estimator used to measure bispectrum provides as output a non trivial convolution between the underlying bispectrum with the window function. This effect should then be included in the theoretical prediction resulting in a 6-dimensional integral that needs to be evaluated in fast way so that it can be implemented in a likelihood analysis. I will present an exact and efficient method to perform the bispectrum-window convolution via Hankel transform [arXiv: 2203.04174] and conclude with possible applications and future directions.

THURSDAY

 

 

BREAKFAST 9:30-10:00

 

Session on GR effects (10:00-11:00 & 11:30-12:45,  chair: Glenn Starkman)

- Obinna Umeh (ICG, Portsmouth, UK). Thursday 10:00-10:45 (yellow room, remote).

Title: Coordinate choice and galaxy bias in the presence of general relativistic effects and primordial non-Gaussianity

Abstract: The local galaxy bias formalism relies on the energy constraint equation at the formation time to relate the metric perturbation to the matter density field. In the Newtonian approximation, this relationship is linear, which makes it easier to specify the initial galaxy density as a function of local physical operators. In general relativity, however, the relationship is intrinsically nonlinear and there is a modulation of the short-wavelength mode by the long-wavelength mode. I will describe in detail why a local coordinate system is needed to specify the galaxy density as a function of local physical operators. I will also describe how to obtain a suitable local coordinate system and how to use the local coordinate to remove the spurious nonlinear coupling between the long and short-wavelength modes both in the presence and absence of the primordial non-Gaussianity.

 

- Miguel Enríquez Vargas (UNAM, Ciudad de México, México). Thursday 10:45-11:00.

Title: Including relativistic and primordial Non-Gaussianit y contributions in cosmological simulations by modifying the initial condition

Abstract: We present a method to implement relativistic corrections, as well as PNG parameters in the evolution of dark matter structures in Newtonian simulations of a LCDM universe via the initial conditions. We take the nonlinear correspondence between the Lagrangian (Newtonian) evolution of dark matter inhomogeneities and the synchronous-comoving (relativistic) matter density description, and use it to promote the relativistic constraint as the initial condition for numerical simulations of structure formation. We implement the relativistic, fNL and gNL contributions as initial conditions for the 2LPTic code which can be an input for L-PICOLA or Gadget, and compute the power spectrum and bispectrum of the evolved matter field. We focus specifically on the case of largest values of non-Gaussianity allowed at 1-sigma by Planck observations(fNL=-4.2 and gNL=-7000). As a checkup, we show consistency with the one-loop perturbative prescription and with a fully relativistic simulation (GRAMSES) on the adequate scales. Our results confirm that both relativistic and PNG features are most prominent at very large scales and for squeezed triangulations.

 

COFFEE 11:00-11:30

- Camille Bonvin (University of Geneva, Switzerland). Thursday 11:30-12:15 (yellow room).

Title: Measuring the distortion of time with large-scale structure

Abstract: To test the theory of gravity we need to test, on one hand, how space and time are distorted by matter and, on the other hand, how matter moves in a distorted space-time. Current observations provide tight constraints on the motion of matter, through redshift-space distortions, but they only provide a measurement of the sum of the spatial and temporal distortions, via gravitational lensing. In this talk I will present a novel method to measure the time distortion on its own, and I will show that it will be detectable by future surveys like the SKA. I will then discuss new tests of gravity that can be built from this measurement.

 

- Mike Shengbo Wang (University of Edinburgh,  Edinburgh, UK). Thursday 12:15-12:30.

Title: Challenges in Primordial Non-Gaussianity Constraints from Galaxy Clustering Power Spectrum and Bispectrum

Abstract: Primordial non-Gaussianity (PNG) offers a unique probe of the dynamics of the very early Universe and leaves an imprint in the large-scale structure (LSS) we see today. However, extracting PNG signals from the distribution of LSS tracers faces numerous challenges, some of which we address in this talk. Firstly, we present our study of the evolution and magnification biases from the eBOSS quasar sample, and assess their importance in modelling the relativistic contributions to the clustering power spectrum, which may hamper PNG detection. Secondly, we propose an alternative hybrid basis appropriate for clustering analyses of large wide-angle galaxy surveys, both alleviating the effect of survey geometry and encapsulating the aforementioned relativistic effects. Thirdly, we present the latest update on the bispectrum analysis of the ongoing DESI survey, which complements PNG detection from the power spectrum.

-Thomas Montandon (Department of Astrophysics, University of Vienna, Vienna, Autria). Thursday 12:30-12:45.

Title: Relativistic second-order initial conditions for simulations of large-scale structure

Abstract: One of the main challenges of cosmology is to understand the physics of the early universe. One way to probe this early period is the study of primordial non-Gaussianity (PNG) through the bispectrum of the matter distribution. The future large-scale structure (LSS) surveys are expected to provide a precise measurement of the distribution of matter in the late universe and therefore add more constraints on PNG. For this purpose, one needs to understand the full evolution of the perturbations beyond the linear theory since the LSS formation is a non-linear process. Among all the non-linearities generated, the relativistic effects, as well as the early radiation effects, are well-known contaminants of the PNG. In this talk, I will explain how we can simulate the large-scale structure of the universe with the N-body simulation ?gevolution? by accounting for all the relevant second-order relativistic non-linearities generated from the primordial epoch to the initial redshift of the simulation. This is a crucial step for the estimation of the systematic effects affecting the PNG.

LUNCH BREAK 12:45-15:00

Discussion: PNG and consistency relations (14:45-15:45 , moderator:  Lucas Pinol) 

Panelists: 

- Fabian Schmidt (MPA, Garching, Germany).

COFFEE 15:45-16:15

LSS (-future) session V (16:15-17:30, chair: Héctor Gil Marín)

Title: Local Primordial Non-Gaussianity from the SPHEREx all-sky survey

Abstract: The scale dependent bias of galaxy density contrasts is an important signal to be extracted in constraining local primordial non-Gaussianity (f_NL (local)) from observations of large scale structure. Constraints so obtained rely on the assumption that horizon-scale features in the linear galaxy bias are exclusively due to primordial physical mechanisms. However, we now know that non-primordial sources of scale-dependent bias do introduce their own horizon-scale signatures - presenting a potential systematic effect that needs to be incorporated in the theoretical modelling of the galaxy power spectra. We investigate the effect of two such sources of scale dependent bias - the free-streaming of light relics and fluctuations in the background of ionizing radiation - on the forecast constraints on local primordial non-Gaussianity obtained from the SPHEREx all-sky survey. Our work quantifies the importance of accounting for these non-primordial systematic effects in improving our constraints on f_NL (local) from future galaxy surveys.

 

FRIDAY

 

 

BREAKFAST 10:00-10:30

 

Theory -GW Session (10:30-12:30, Chair: Sebastián Cespedes)

-  Marco Peloso (University of Padova, Italy). Friday 10:30-11:15 (yellow room).

Title: Non-Gaussian scalar and tensor modes from particle production during inflation

Abstract: We discuss the phenomenology of particle production occurring either as discrete episodes or continuously throughout inflation. These process lead to sourced density perturbations and gravitational waves. The former modes can in some cases be the seeds of primordial black holes (PBHs). We study the abundance of PBHs formed in models in which an axion is coupled to gauge fields, and the unavoidable stochastic gravitational field background (SGWB) that accompanies the presence of these PBHs. The anisotropies of the sourced SGWB (with or without the presence of PBHs) can be a novel probe of primordial non-Gaussianity. We study the 2- and 3-point correlations functions of sourced scalar and tensor modes, and, in particular, we discuss the detectability of this SGWB. We conclude with a discussion of the stability of models in which the particle production is so strong as not only to produce visible scalar and tensor perturbations, but also to significantly impact the background dynamics. 

- Ameek Malhotra (UNSW Sydney, Sydney, Australia). Friday 11:15-11:30.

Title: Gravitational wave anisotropies as a probe of primordial non-Gaussianity

Abstract: Stochastic gravitational wave backgrounds (SGWB) can be generated by a variety of processes in the early universe, most notably inflation. These backgrounds are characterised in terms of their spectral shape, polarisation, (non-)Gaussianity and anisotropies. In this talk I will show how the anisotropies of the inflationary SGWB could be used to constrain primordial ultra-squeezed non-Gaussianity in the tensor sector and potentially probe the inflationary particle content. I will present projected constraints on the corresponding non linearity parameter F_NL for several upcoming GW detectors and also highlight how the angular dependence of the primordial bispectrum affects these constraints. The angular dependence may be a signature of additional spinning fields present during inflation. This talk will be based on arxiv:2012.03498 and 2109.03077.

- Lucas Pinol (IFT, Madrid, Spain). Friday 11:30-11:45.

Title: Primordial non-Gaussianities and gravitational waves: an intertwined story

Abstract: Notoriously, scalar Primordial Non-Gaussianities (PNG) constitute a key prediction of the inflationary paradigm that is yet to be discovered. Less famous, tensor non-Gaussianities as well as mixed scalar-tensor non-Gaussianities may also arise from non-linear interactions in the early Universe. I will explain how the Stochastic Gravitational-Wave Background (SGWB) may be used as an additional source of information about different kinds of PNG, independently of CMB and LSS experiments. I will consider two specific examples of such physical phenomena:

 1. I will explain how anisotropies in the SGWB can be computed rigorously using the in-in formalism and how they are related to the squeezed limit of primordial scalar-tensor-tensor (STT) and tensor (TTT) bispectra.

 2. I will show that scalar-induced gravitational waves can be sourced by the scalar trispectrum (SSSS), but I will explain that this contribution should be small in scale-invariant scenarios for theoretical consistency.

Title: Small-scale tests of inflation

Abstract: The detection and characterisation of primordial gravitational waves produced during inflation can be an excellent test for the particle content of the very early universe. We consider an inflationary realisation whose tensor spectrum is sourced already at linear order, with a sufficient production of primordial gravitational waves to make the signal detectable at interferometer scales. We then focus on the tensor non-Gaussianities that ensue from the same configuration. On small-scales, anisotropies induced in the tensor power spectrum by long-short modes coupling become the key handle on (squeezed) primordial non-Gaussianities. We identify the parameter space generating percent level anisotropies at scales soon to be probed by SKA and LISA.

- Giorgio Orlando (University of Groningen, Groningen, Netherlands). Friday 12:00-12:15.

Title: Imprints of parity violation in gravitational waves V modes

Abstract: According to the standard paradigm, parity is a fundamental symmetry of our Universe. However, a recent analysis of the BOSS data suggests violation of parity in the galaxy 4pt function. If not the result of a systematic, this signature can be explained only if parity is violated at non-linear level by some mechanism arising during inflation. In this presentation I will outline the classical cosmological correlators that can lead to observational signatures of parity violation in primordial non-Gaussianities. I will discuss how V-mode gravitational waves anisotropies can be used as a new observational channel to measure parity-violation in squeezed primordial bispectra.

- Oksana Iarygina ( Nordita, Stockholm, Sweden ). Friday 12:15-12:30.

Title: Inflation with spectator Gauge-flation

Abstract: This talk describes the viability of inflation with a spectator sector comprised of non-Abelian gauge fields coupled through a higher order operator. I will discuss the theoretical restrictions for the amplitude and tensor tilt for chiral gravitational waves as well as the maximum possible enhancement of the gravitational wave background with respect to the one coming from vacuum fluctuations.

- Caner Unal. Friday 12:30-12:35 (5min).

Title: PNG from induced GWs

LUNCH BREAK 12:30-14:30

CMB session Il  (14:30-16:30. Chair: Juan García-Bellido)

- Glenn Starkman (CWRU, USA).  Friday 14:30-15:15 (yellow room).

Title: Statistical anisotropy or non-Gaussianity

Abstract: There is already considerable evidence that the CMB temperature maps do not represent a typical realization of a Gaussian random statistically isotropic field. If this reflects new underlying physics, does it tell us that the universe is statistically anisotropic, non-Gaussian, or both? If instead we posit that we live in a highly anomalous realization, how and when can we discover non-Gaussianity?

- Guadalupe Cañas Herrera (Leiden University, Leiden, Netherlands). Friday 15:15-15:30.

Title: How to reconstruct the inflaton's speed of sound using Cosmological data

Abstract: Observations of Planck's CMB favour a canonical slow-roll single-field scenario for inflation. However, simple multifield extensions can also explain the current data. We present our search for multifield-motivated extra degrees of freedom in the context of an effective single field theory with a varying speed of sound cs of the adiabatic mode. Transient reductions in cs produce deviations (or "features") in the primordial power spectrum of scalar perturbations as well as in higher-order correlation functions (i.e: the bispectrum). Features of sufficient intensity may be observed in the CMB angular power spectrum (T and E), and in the power spectrum of galaxy clustering and weak lensing. To further analyse features using galaxy clustering data, we need to study the impact bispectrum features have on the scale-dependent bias of galaxy clustering. We present a standard methodology based on Gaussian Processes for general Bayesian.

- J. Richard Bond (CITA, Canada). Friday 15:30-15:45.

Title: Intermittent nonGaussian Transport from Inflation-epoch Generation to Cosmic Web Probes

Abstract: A major CITA concentration is concentrated nonG which can arise generically during and after inflation from field-instabilities transverse to the inflaton. CMB and LSS Webskys we construct with large spatially localized pNGs can evade the stringent 2D perturbative single-template constraints from the ~10 e-folds probed by Planck and other CMB experiments, 1. may play a role in the low-k CMB anomalies, 2. are more easily detected in 3D Large Scale Structure Surveys, and 3. could be hugely-big in the largely obscured 50 e-foldings from CMB/LSS scales to the end-of-inflation. At CITA our program is to use pseudo-spectral lattice simulations and dynamical systems theory to characterize the theoretical possibilities, manifested by bursty entropy and collective-particle creation, and nonlinearly propagate them to correlated emission maps, probe-able for the underlying pNG via novel component-separated statistical methods. We have applied our multi-field effective-potential surface framework to slow-growth instabilities after inflation ends and to short-lived instabilities while inflation is ongoing using an in-out state formulation for the simulations. Though similar in spirit to the mass^2->0 cosmic collider program, the mass^2 <0 in phase transitions make much more dramatic and observable phenomena. Our detailed results, further elucidated in a companion talk by Tom Morrison, compress onto nonlinear-bias entropy maps of transverse nearly Gaussian fields that lead to intermittent peaks, easily realizable for propagation to the here and now. We even get entropic memory of domain wall and stringy structures that can pass though to the Webskys.

- Thomas Morrison (CITA-University of Toronto, Toronto, Canada). Friday 15:45-16:00.

Title: A Tale of Tails: Memories of Phase Transition Instabilities During Inflation and Intermittent nonGaussianity

Abstract: Using high precision lattice field simulations of the dynamics of fully nonlinear systems we compute the response in $\zeta$, and its nonGaussianity in particular, which can be isolated even if extremely small. This allows us to move beyond conventional perturbative characterizations of nonG into unveiling novel yet generic forms. Here we focus on a systematic exploration of a broad class of models in which temporary spontaneous symmetry breaking features in the effective potential induce a short-lived instability in a field transverse to the inflaton. This causes fluctuations to grow and enter the nonlinear regime before relaxing once the symmetry breaking feature has been past. The derived $\zeta$ nonG can be quite large yet uncorrelated with an underlying stochastic-inflation Gaussian contribution associated with featureless potentials. Paradoxically, multiple-sourcing in weak instabilities which lead to conventional perturbative nonG can be the most complex, mixing and entangling nonG sourced through multiple channels at similar levels of significance As the strength of the instability is increased we identify a strong simply-characterizable coherent contribution which emerges to dominate the conventional stochastic nonG, manifested as sparse concentrated peaks, leading to extended tails in the one-point and peak distribution functions and phase coherences far in excess of those for Gaussian random fields. Increasing the strength of the instability still further drives the phase transition in the transverse field towards completion in advance of relaxation, with peaks merging to imprint a memory of the domain wall network temporarily formed in the transverse field.

- Nathan Carlson (University of Toronto, Toronto, Canada). Friday 16:00-16:15.

Title: Unveiling novel primordial non-Gaussianity with the Peak Patch-Websky simulations of the cosmic web

Abstract: Observables of primordial curvature non-Gaussianities (PNG) are needed to test multi-field inflation models of the early universe, that is all inflation models. The classic CMB constraints on single-template fNL from the bispectrum only scratch the surface of possibilities. The Peak Patch-Websky pipeline successfully used for very large CMB and LSS mocks of lensing, tSZ, kSZ, CIB and other correlated emission maps in standard models of cosmology, shown to be quite accurate over the years, is extended to transport novel PNG forms through to observables. In this work, we present simulated sky maps of intermittent, uncorrelated PNG models, non-Gaussian spikes that arise during inflation from chaotic billiards effects in preheating, and a new extended stochastic inflation model motivated by an ambitious suite of high-accuracy lattice simulations of early-universe field theories presented in the related talk by Tom Morrison, and compare them with varieties of correlated and un-correlated fNL. These uncorrelated models lead to PNG with amplitudes not confined by the tight constraints on classical fNL, demonstrating that new parameter space of inflation models can be tested against observations with these simulations. Our new non-Gaussian pipeline is fast as PNGs are implemented as nonlinear functions of Gaussian fields, and only low-order solutions to the equations of motion are required to model highly dynamical halos as patches moving through a weakly non-linear background. We can generate maps at orders of magnitude less computational expense than N-body simulations, a degree of efficiency that will be critical in validating our theories with new data as gigaparsec-scale surveys come online in the coming years.

- Wuhyun Sohn (KASI, Korea). Friday 16:15-16:30.

Title: CMB-BEst: a high-resolution CMB bispectrum estimator for future surveys

Abstract: The CMB bispectrum has provided one of the most stringent bounds on primordial non-Gaussianity, and the constraints are expected to improve further with future surveys. After a brief review of the CMB bispectrum estimation process, we present our newly developed bispectrum estimator which utilizes a set of general basis functions and is able to accurately constrain models with oscillations. The code, named CMB-BEst, is highly optimised and parallelised for high-performance computing clusters. We show the results of validation tests on internal consistency and comparisons against Planck’s Modal estimator. CMB-BEst’s flexibility and precision will allow both general and targeted analyses of previously unconstrained models. We provide some proof-of-concept examples and discuss the prospects and challenges ahead.

COFFEE 16:30-17:00

Discussion: Future of PNG (17:00-18:00 , moderator:  )