16 OCT 2019
13:30 - 15:00

In this talk, we first review the idea of mimetic gravity and show how dark matter naturally arises in this scenario in the cosmological background. We show that the setup is unstable at the level of perturbations and we will introduce some possible healthy extensions of this scenario. Replacing the scalar field with a general p-form, in the second part, we find a new mimetic theory and we particularly focus on the case of one-form gauge potential. This model is free of instabilities and provides an energy density which behaves like the spatial curvature in the cosmological background.

16 OCT 2019
14:00 - 15:00

Seminar Room (classroom A), Farmanieh Building, IPM

16 OCT 2019
14:00 - 15:00

An overview of distributed algorithms and a distributed constant approximation factor algorithm for finding minimum dominating set of planar graphs

16 OCT 2019
15:30 - 16:30

We are going to talk about a two-dimensional model in statistical mechanics, the double-dimer model, which is simply a straightforward generalization of the dimer model. The latter is well-known in both physics and mathematics because of its particular features and substantial relations to many contexts, known in combinatorics as a perfect-matching problem. Here the emphasis is on the critical behavior of the loop ensembles of the double-dimer model, conjectured to converge to the level sets of the Gaussian free field and Schramm-Loewnerevolution or conformal loop ensembles with parameter 4. We use the Grassmannian representation of the dimer model to compute some loop-related observables in rectangular domains on the square lattice. The asymptotic behavior of the results in the continuum turns out to be consistent with previously known ones or with the aforementioned conjecture.

16 OCT 2019
15:00 - 16:00

Abstract:The Sachdev-Ye-Kitaev (SYK) model is an interacting statistical quantum mechanical model. In low temperature, this model has a (1+1)-dimensional dilaton-gravity description in AdS_2 spacetime. The key link between gravity and field theory side is the boundary effective action denoted as "Schwarzian theory".
In this talk after reviewing this construction, we set up this correspondence in the case of (1+1)-dimensional dilaton-gravity in flat spacetime and derive the analogous boundary action which coincides with the one discovered recently in1908.08089 as "warped Schwarzian theory".



The talk is base on: https://arxiv.org/abs/1909.04060


Larak Seminar Room

17 OCT 2019
11:00 - 12:00

Abstract: In the vacuum state of a CFT, the entanglement entropy of singular surfaces contains a logarithmic universal term which is only due to the singularity of the entangling surface. We consider the relevant perturbation of a three-dimensional CFT for the singular entangling surface. We observe that in addition to the universal term due to the entangling surface, there is a new logarithmic term which corresponds to a relevant perturbation of the conformal field theory with a coefficient depending on the scaling dimension of the relevant operator. We also find a new power-law divergence in the holographic entanglement entropy. In addition, we study the effect of a relevant perturbation in the Gauss-Bonnet gravity for a singular entangling surface. Again a logarithmic term shows up. This new term is proportional to both the dimension of the relevant operator and the Gauss-Bonnet coupling. We also introduce the renormalized entanglement entropy for a kink region which in the UV limit reduces to a universal positive finite term.


Larak Seminar Room

21 OCT 2019
16:00 - 18:00

The perils of benevolence

23 OCT 2019
15:30 - 17:30

We show that Martin's Maximum${}^{++}$ implies Woodin's ${mathbb P}_{ m max}$ axiom ($star$). This is joint work with David Aspero.

12 DEC 2019
-

Farmanieh Conference Hall