High Energy Theory

# Events

The purpose of this meeting is to bring together experts working at the interface of cosmology, string theory and particle physics for a few days of informal talks and exchanges of ideas. The schedule will allow ample time for impromptu discussions and collaborations. Each talk includes ~60mins worth of presentation and interruptions, plus 30mins worth of questions/discussions.

Place: DRL 4N12

Thursday, December 3:

10:30-11am: Welcome coffee

11am-12:30pm: Juan Maldacena (IAS)

12:30pm-2pm: Catered lunch (in 4N12)

2-3:30pm: Erik Verlinde (Amsterdam)

3:30-4pm: Coffee

4-5:30pm: Liam McAllister (Cornell)

6:30pm: Conference dinner at Han Dynasty

Friday, December 4:

10:30-11am: Welcome coffee

11am-12:30pm: Gregory Gabadadze (NYU)

12:30pm-2pm: Catered lunch (in 4N12)

2-3:30pm: Savdeep Sethi (Chicago)

3:30-4pm: Coffee

4-5:30pm: Mariangela Lisanti (Princeton)

End of the workshop

Time: 2pm
Place: 2N36

Title: F-Theorem and the Epsilon Expansion
Abstract:
I will discuss the dimensional continuation of the sphere free energy in conformal field theory. This provides an interpolation between a-anomaly coefficients in even dimensions and F-values in odd dimensions, and smoothly connects the existing a-theorems and F-theorems. As concrete applications, I will explain how to use the Wilson-Fisher epsilon expansion to find the value of F for the 3d Ising CFT and related O(N) symmetric models, and for the conformal phase of the 3d QED with N_f massless fermions.

Time: 2pm
Place: 2N36

Title: Witten Diagrams Revisited: The AdS Geometry of Conformal Blocks

Time: 2pm
Place: 2N36

Title: Matter Transitions and Heterotic/F-theory duality

Abstract:

We explore a novel type of transition in certain 6D and 4D Heterotic/F-theory dual pairs, in which the matter content of the theory changes while the gauge group and other parts of the spectrum remain invariant. Such transitions can occur, for example, for SU(6), SU(7), and SU(8) gauge groups, where matter in a three-index antisymmetric
representation is exchanged in the transition for matter in a
two-index antisymmetric representation. These matter transitions are
realized by passing through superconformal theories at the transition
point. We also briefly describe some other situations,
with groups such as Sp(3), SO(12), and SU(3), where analogous matter
transitions can occur between different representations.  For SU(3),
in particular, we find a matter transition between adjoint matter and
matter in the symmetric representation, giving an explicit Weierstrass
model for the F-theory description of the symmetric representation
that complements other recent analogous constructions.

Time: 2pm
Place: 2N36
Title: The Future is Stochastic
Abstract: Precision calculations in de Sitter space (such as of inflationary predictions for primordial fluctuations) are often plagued by infrared problems and issues of secular time dependence. Similar issues about the breakdown of perturbation theory also arise for information loss in black holes. This talk briefly summarizes what is known about when these problems do (and do not) arise, and how similar problems are dealt with in other areas (like optics). It is argued that Master-Equation techniques used there also apply to cosmology (and possibly black holes) and can tell us how to extract reliably late-time predictions. Applied to inflation they lead to Starobinsky's stochastic methods (plus potential corrections). This is argued to provide an explanation for why stochastic inflation seems to resum IR effects in simple examples, and allows these tools to be generalized to other systems. I mention in passing the relevance of these tools to the problem of Schrodinger's Cosmologist! : how primordial fluctuations decohere sometime between their production during inflation and their observation early in the present Big Bang Epoch.

Time: 2pm
Place: 2N36
Title: "Effective string theory for vortex lines in fluids and superfluids"

Time: 2pm
Place: 2N36
Title: “Thriving from the vacuum”
Abstract: Theories of modified gravity in the infrared usually come hand in hand with additional degrees of freedom which couple to matter at gravitational strength and carry a low strong-coupling scale. By including non-trivial effects from the vacuum I will show how the strong-coupling scale can be raised while keeping the theory fundamentally Lorentz-invariant. This can lead to new features and may alleviate the need for a screening mechanism.

Time: 2pm
Place: 2N36

Time: 2pm
Place: 4N9
Title: Black Holes in Higher-Derivative Gravity and Einstein-Scalar Gravity

Title:  Incidence geometry and resolutions of Weierstrass models

Time: 2pm
Place: 4N9

Abstract: In this talk, I  will present several new results in the geometry of elliptic fibrations:
In the first part of the talk, I  will introduce an incidence geometry described by a representation of a given Lie algebra and explain how it contains a natural poset structure reminiscent of a Gelfand-Tsetlin pattern. This poset provides  a simple counting of flats and ensembles of the incidence geometry. For an elliptic fibration, it is understood as a counting of (partial) crepant resolutions.  In a physical context, the counting is interpreted as a detailed  enumeration of mixed Coulomb-Higgs branches of a five dimensional gauge theory with 8 supercharges.   In particular, I will present a  generating function counting the  mixed Coulomb-Higgs phases of a U(n) gauge theories with matter in the fundamental and anti-fundamental representations.
In the second part of the talk, I will describe the network of crepant resolutions of a SU(2) SU(3)  gauge theory modeled by an elliptic fibration. This provides a fully resolved description of models studied recently by Grassi-Halverson-Shanesonn-Taylor. I will explain how representation theory aspects are retrieved by a simple analysis of intersection numbers.

Time: 2pm
Place: 2N36
Title: Resurgence in quantum field theory: handling the Devil's invention.
Abstract:Renormalized perturbation theory for QFTs typically produces divergent series, because the series coefficients grow factorially at high order. It has been a historical challenge to understand the asymptotic nature of perturbative series, and it has been unclear in what precise sense semiclassical expansions capture the physics of even weakly-coupled QFTs. I will discuss a recent conjecture that the semiclassical expansion of path integrals for asymptotically free QFTs yields well-defined answers once the implications of resurgence theory are taken into account. Resurgence theory relates expansions around different saddle points of a path integral to each other, and has the striking practical implication that the high-order divergences of perturbative series encode precise information about the non-perturbative physics of a QFT. These ideas will be discussed in the context of several QCD-like theories, where systematic semiclassical control over the dynamics is achieved using adiabatic compactifications on a circle. Fitting a conjecture by ’t Hooft, understanding the origin of the notorious renormalon divergences of perturbation theory of asymptotically-free QFTs allows us to see the microscopic origin of the mass gap of these QFTs in the semiclassical domain.

Time: 2pm
Place: 2N36
Title: New Ekpyrotic Quantum Cosmology
Abstract: This talk will present recent results in the quest to construct a viable cosmological model devoid of singularities and infinities. More specifically: the no-boundary proposal provides a compelling theory for the initial conditions of our universe. In this context, the recently discovered ekpyrotic instantons describe the creation of a classically contacting universe out of nothing. One notable consequence is that the ekpyrotic attractor can explain how the universe became classical. However, up to now these instantons ended in a big crunch singularity. We show how this can be remedied by adding higher-derivative terms, allowing a smooth bounce into an expanding phase to take place. Remarkably, and although there is a non-trivial evolution during the bounce, the wavefunction of the universe is classical'' in a WKB sense just as much after the bounce as before. These new non-singular instantons can thus form the basis for a fully non-singular and calculable (ekpyrotic) history of the universe, from creation until now.

Time: 2pm
Place: 2N36

Time: 2pm
Place: 4N36

Title: Shifting around cosmology

Time: 2pm
Place: 2N36

Title: Logarithmic Corrections to Black Hole Entropy V2.0

Time: 2pm
Place: 2N36

Title: New ghost-free matter couplings and derivative interactions in massive gravity and multigravity

Time: 2pm
Place: 2N36

Time: 2pm
Place: 2N36

Title: Living beyond the edge -- Higgs inflation, metastable vacua, and importance of radiative corrections

Time: 2pm
Place: 2N36
Abstract: The measurements of the Higgs mass and the top Yukawa coupling indicate that we live in a very special Universe, at the edge of the absolute stability of the electroweak vacuum. While fully stable situation allows for simple Higgs Inflationary setup, boundary and unstable situations turn out to be also very interesting, and also allow for inflation and successful Universe evolution. The key point is taking into account radiative corrections to the couplings at the energy scale $M_P/\xi$. Then, the inflationary potential can appear even for metastable SM vacuum, and the temperature potential at preheating prevents the Universe to settle in the high scale vacuum.

Title: Self-dual strings of six-dimensional SCFTs
Time: 2pm
Place: 2N36

Abstract: A distinctive feature of six-dimensional superconformal field theories is the existence of self-dual strings whose interactions encode the SCFTs' dynamics. A deep understanding of these SCFTs is still lacking, primarily due to a poor understanding of the properties of their strings, which are intrinsically strongly-coupled and can form bound states. I will explain how in several cases (including the theory of N+1 parallel M5 branes and the theory of a small E8 instanton) the strings can be described by suitable two dimensional quiver gauge theories. In particular, this makes it possible to compute the elliptic genera of these strings and of their bound states. For SCFTs for which a quiver gauge theory description is not available, I will explain how topological string theory still provides a way to study the corresponding strings.