Upcoming Theory Seminars*
Speaker: Neil Weiner, NYU
Title: "SUSY WIMPs and Higgses with nearby strong dynamics"
Speaker: Bart Horn, Columbia University
Title: "Uplifting AdS/CFT to Cosmology"
I will discuss recent work using brane constructions to uplift AdS/CFT
dual pairs to de Sitter and FRW solutions. We find a microscopic
realization of the semi-holographic "de Sitter/de Sitter correspondence"
of Alishahiha et al., and we express the de Sitter horizon entropy in
terms of the microscopic parameters. We consider potential consequences
of uplifting for the dual description, specifically effects of time
dependence and moduli stabilization in the bulk on the RG flow in the
dual picture. For de Sitter, the maximal symmetry greatly simplifies
the RG flow, which we hope may help point the way towards an explicit
Speaker: Gaston Giribet, University of Buenos Aires
Title: "SO(8) symmetry and triality of N=2 super Yang-Mills and the 2d/4d correspondence"
After briefly reviewing the correspondence between 2d conformal field
theories and 4d superconformal gauge theories, I will discuss how the
global symmetry of N=2 super Yang-Mills theory with Nf=4 flavors in d=4
dimensions can be seen to emerge from the Liouville theory description
via the so-called Alday-Gaiotto-Tachikawa correspondence. This
represents a non-trivial check of the conjectures involved as it follows
from a priori unexpected identities of Liouville theory. I will also
comment on recent attempts to describe non-fundamental surfaces
operators within this framework.
Federico Piazza, Paris Center for Cosmological Physics, Laboratoire APC
Title: "The effective field theory of dark energy"
I will talk about a very recent in collaboration with Giulia Gubitosi
and Filippo Vernizzi, where we a formalism previously applied to
inflation and propose a universal description of dark energy and
modified gravity that includes all single-field models. We consider the
metric universally coupled to matter fields and we write in terms of it
the most general unitary gauge action consistent with the residual
unbroken symmetries of spatial diffeomorphisms. Our action is
particularly suited for cosmological perturbation theory: the background
evolution depends on only three operators. All other operators start at
least at quadratic order in the perturbations and their effects can be
studied independently and systematically. In particular, we have focused
on the properties of a few operators which appear in non-minimally
coupled scalar-tensor gravity and galileon theories and studied the
mixing between gravity and the scalar degree of freedom that they
produce. The scalar can always be de-mixed from gravity at quadratic
order in the perturbations, but not necessarily through a conformal
rescaling of the metric. I will also mention how to ``translate" several
explicit models in our language.
Speaker: Gabriele Veneziano, College de France
Title: “Transplanckian collisions of particles, strings and branes: what can (have) we learn(ed)?”
I will give an overview on what we have learned so far on
transplanckian-energy collisions of particles, strings, and branes,
mention some open problems, and speculate on what we hope to learn in
the near future from these gedanken experiments.
Speaker: Raman Sundrum, University of Maryland
"Metaphor for Dark Energy"
At the beginning of the twentieth century, there arose two distinct
means of extending Newton's Law of Gravity and the Equivalence Principle
to the relativistic regime. Of course one was General Relativity. The
other was Nordstrom's theory of scalar gravity, improved further by
Einstein and Fokker as a theory of curved spacetime. This theory
ultimately failed observational tests of relativistic gravity, but it
has come up in other guises in theoretical physics over the decades. I
will describe this remarkable theory and update it into the era of
quantum mechanics and string theory, and point out that it can provide a
simpler "laboratory" for thinking through some tough puzzles of real
gravity. In particular I show that scalar gravity has a strikingly
faithful version of the cosmological constant problem, satisfying the
same no-go "theorems" of real gravity, and yet there is an elegant
solution in terms of a subtle form of evolving "dark energy" that can be
understood in standard quantum field theory.
Speaker: Koenraad Schalm, Institute-Lorentz for Theoretical Physics Leiden University
Title: "Strongly coupled electron systems from holography and the birth and collapse of anti-de-Sitter stars"
The application of the holographic AdS/CFT correspondence to condensed matter systems has shown us remarkable new insights into strongly coupled quantum matter. It provides a novel quantum critical origin of superconductivity that lies outside BCS theory; and it is holographically able to describe non-Fermi liquids as directly observed in experiments in strongly correlated electron systems. In the pursuit of a holographic construction as close to a real quantum critical electron system as possible, I will discuss how the inherent quantum nature of bulk AdS fermions, dual to 1/N corrections in the field theory, is essential to capture the correct physics, and show how the descent of the strongly coupled fermi state into the novel holographic superconductor is described by the collapse of a "star" in anti-de-Sitter space.
Speaker: Michael Buchoff, Lawrence Livermore National Laboratory
Title: "Composite Dark Matter Exclusions from the Lattice"
One intriguing coincidence in cosmology is how the observed dark matter
and baryonic densities are within a factor of 5 in magnitude. A natural
explanation for such a coincidence is that the origin of the dark
matter density is intimately related to the early universe processes
that led to the baryon asymmetry. The majority of these “asymmetric”
dark matter scenarios favor a strongly coupled composite sector ala QCD,
where neutral, long-lived composites can survive to be observed today,
but still have charged constituents to interact with early universe
baryogenesis. As a result, these neutral composites are expected to
have non-zero electromagnetic properties, such as magnetic moments,
charge radii, and polarizabilties, which can be observed in direct
detection experiments. The values of these properties are inherent to
the dynamics of these strongly coupled theories, where non-perturbative
lattice methods allow for a reliable exploration with controlled
systematics. In this talk, I will present some initial results for a
three-color, QCD-like theory with two and six light fermion flavors,
including implications on the latest exclusions from the Xenon100
Speaker: Kurt Hinterbichler, Perimeter Institute for Theoretical Physics
Title: "Partially Massless Gravity"
On de Sitter space, there exists a special value for the mass of a
graviton for which the linear theory propagates 4 rather than 5 degrees
of freedom. If a fully non-linear version of the theory exists and can
be coupled to known matter, it would have very interesting properties
and could solve the cosmological constant problem. I will describe
evidence for and obstructions to the existence of such a theory.
Speaker: Raphael Bousso, UC Berkley
"Is there an alternative to firewalls?"
*Please continue visiting the Department of Physics web site for seminar updates.