GRASS family and friends "almond tree" Meeting
Speakers
Name 
Institution 
Talk 
Alonso , David 
U. Oxford 

Bueno , Pablo 
KU Leuven 
Einsteinian cubic gravity, black holes and holography 
Guarino , Adolfo 
U. Libre de Bruxelles 
Holographic RG flows from massive IIA 
HerreroValea , Mario 
É.P.F. de Lausanne 
Flowing to NoGR 
Jiménez , Amadeo 
U. Jena 
Music for the holographic party 
MartínLozano , Víctor 
U. Bonn 
Constraining the SM and Beyond from the Weak Gravity Conjecture 
Montero , Miguel 
U. Utrecht 
Are tiny gauge couplings out of the Swampland? 
Ramírez , Pedro F. 
U. de Milano 
On the construction of (symmetric) microstate geometries 
Regalado , Diego 
CERN 
Engineering N=4 theories in four dimensions 
Shahbazi , Carlos 
U. Hamburg 
On the spin geometry of Mtheory 
Soler , Pablo 
U. Wisconsin 
Black hole entropy corrections from charged fields 
11 results 
I will start with an overview of various recent developments in the area of higherorder gravities and
their black hole solutions, which have led to the discovery of a new type of theories which generalize the
Lovelock class. Then, I will focus on Einsteinian cubic gravity (ECG) which, in a sense I will make
precise, provides a canonical modification of Einstein gravity in D=4, analogous to the one produced by
GaussBonnet in D>4. I will discuss two applications. Firstly, I will explain how ECG (and its cousin
theories) drastically modify the evaporation process of black holes. And second, I will show that ECG
provides a nonperturbative toymodel for a nonsupersymmetric holographic CFT (analogous to
Quasitopological gravity in d=4) in three (boundary) dimensions and discuss some of its properties.
Dimensional reduction of supergravity theories on spheres plays a central role in the
gauge/gravity correspondence. Prominent examples are the reductions of elevendimensional supergravity on
S7 and type IIB supergravity on S5 which are dual to ABJM and N=4 SYM theories, respectively. Using the
recently discovered duality between massive IIA supergravity on S6 and super ChernSimonsmatter theories,
we will describe RG flows holographically in terms of domainwall and black hole solutions in the gravity
side.
The problem of quantizing gravitational interactions is related to the nonrenormalizability of the EinsteinHilbert action and the need to include and infinite number of order one operators at energies of about the Planck scale. This has been interpreted as suggesting the existence of new physics at (or below) this scale, which may relax the strong coupling regime, leading to an ultraviolet complete theory.
Here I will take a different approach — the possibility that gravity might undergo a strong coupling phase for a finite range of energies, eventually going back to a weakly coupled theory with a different symmetry realization, represented by the ultraviolet complete version of Hořava gravity.
Dear theoretical physicists,
The last edition of the holographic party was nice but once again the phonons didn't come and there was no music. We all know whose fault it is. So my proposal for this year is simple: let's not invite Lorentz. He has his temper so we should do it in a nonexplicit way. From past experiences we know that this is a nontrivial task, however I must remark that this is an absolute must if we want to come close to something which actually looks like a real party.
Lately some people have been proposing a class of massive gravity holographic models which do the job, I think we should try. It's about time.
It is known that not every effective field theory could be embedded in quantum gravity, but only those which are consistent with the
QG conjectures. Does these constraints have an impact in low energy physics? Recently, Ooguri and Vafa argued using a strong approach of the Weak Gravity Conjecture that nonsupersymmetric stable AdS vacua are incompatible with quantum gravity. It is also known that compactifying the Standard Model to 3 or 2 dimensions can give rise to AdS vacua. Using the fact that those vacua must be absent, several constraints are set on the SM and BSM particles, obtaining a lower bound on the cosmological constant in
terms of the masses of the neutrinos. Moving forward one can translate those into an upper bound for the EW scale around the TeV range.
Consistency with quantum gravity and black hole physics puts significant constraints on
lowenergy effective field theories. In fact, most EFT’s do not satisfy these criteria, and are said to be
in the “Swampland”. Most Swampland constraints remain conjectural, supported mainly by a plethora of
stringy examples. In this talk I will discuss a better supported example of a Swampland constraint, in the
context of the AdS/CFT correspondence: A bound on the gauge coupling of any U(1) theory coupled to gravity
in AdS space. This equivalent to a bound on the twopoint coefficient of holographic large N theories. The
same logic leads to a logarithmic bound involving the gauge coupling, the cutoff of the effective field
theory, the AdS radius, and Planck’s mass.
Microstate geometries are horizonless solitonic solutions of supergravity theories which have
been claimed to correspond to the classical description of particular microstates of a given black hole.
Such solutions are sourced by charges "dissolved in fluxes" threading noncontractible cycles, and for this
reason the construction of explicit generic examples has remained a challenging problem for more than a
decade. In this talk I will present the results of arXiv:1709.03985, where a strategy to sistematically
construct all (symmetric) microstate geometries is proposed.
Known N=4 theories in four dimensions are characterized by a choice of gauge group, and in some
cases some "discrete theta angles", as classified by Aharony, Seiberg and Tachikawa. I will review how
this data, for the theories with algebra su(N), is encoded in various familiar realizations of the theory,
in particular in the holographic AdS_5 \times S^5 dual and in the compactification of the (2,0) A_N theory
on T^2. I will then show how the resulting structure, given by a choice of polarization of an appropriate
cohomology group, admits additional choices that, unlike known theories, generically preserve SL(2,Z)
invariance in four dimensions.
I will explain the classification of bundles of weakly faithful Clifford modules in terms of
Lipschitz structures. As an application, I will prove that, in the presence of an internal Dirac operator,
M theory can only be defined on orientable and spin elevendimensional manifolds. This is work in
collaboration with C. Lazaroiu.
I will discuss one loop corrections to the entropy of ReissnerNordstrom extremal black holes induced by
charged massive particles. When the particles are superextremal, IR divergences in the computation
reflect the instability of the black hole against Schwinger pair production and decay. When superextremal
particles are absent extremal, black holes are stable and charged particles can induce interesting
logarithmic corrections to their entropy. I will suggests possible connections to the Weak Gravity
Conjecture, which demands the existence of (super)extremal particles.
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