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09:30 to 10:00 |
Raghav G. Jha (Syracuse University, USA) |
Recent Results from Lattice Supersymmetry in 2 ≤ d < 4 Dimensions The lattice formulation of supersymmetric theories is important for understanding some important problems in Physics beyond standard model. Certain supersymmetric theories are now possible to study on the lattice using ideas of topological twisting. We will present results from lattice simulations of four-supercharge SYM theory in two dimensions and discuss supersymmetry breaking in this theory. We will then discuss some preliminary results from lattice simulations of finite-temperature sixteen-supercharge SYM in three dimensions at strong couplings and large N and compare it to predictions from its dual supergravity theory.
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10:00 to 10:30 |
David Schaich (University of Bern, Switzerland) |
Lattice N=4 Supersymmetric Yang--Mills Building on the pedagogical lectures introducing supersymmetric lattice field theories, I will discuss ongoing numerical investigations of maximally supersymmetric Yang--Mills (N=4 SYM), the only known four-dimensional theory for which there exists a lattice formulation that exactly preserves a subset of the supersymmetry algebra. I will focus on ongoing lattice studies of the N=4 SYM static potential and conformal operator scaling dimensions, comparing preliminary non-perturbative results with analytic predictions. Time permitting I will also present recent results for the thermodynamics of the dimensional reduction of the theory to N=(8,8) SYM in two dimensions, which holography relates to properties of certain black hole solutions in supergravity.
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10:30 to 11:00 |
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Tea |
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11:00 to 11:30 |
Pallab Basu (ICTS, India) |
Complex Langevin Dynamics in Large-N Matrix Models Using complex Langevin dynamics and stochastic quantization we examine the phase structure of a large N unitary matrix model at low temperature with finite quark chemical potential. This model is obtained as the low temperature effective theory of QCD with N number of colors and N_f number of quark flavors defined on the manifold S^1 X S^3. We simulate several observables of the model, including Polyakov lines and quark number density, for large N and N_f. The action is manifestly complex and thus the dominant contributions to the path integral come from the space of complexified gauge field configurations. For this reason, the Polyakov line eigenvalues lie off the unit circle and out in the complex plane. A distinct feature of this model, the occurrence of a series of Gross-Witten-Wadia transitions, as a function of the quark chemical potential, is reproduced using complex Langevin simulations.
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11:30 to 12:00 |
Andrei Alexandru (The George Washington University, USA) |
Sign Problem and the Generalized Thimble Method Questions about quantum field theories at non-zero chemical potential and/or real-time correlators are often impossible to investigate numerically due to the notorious sign problem. A possible solution to this problem is to deform the integration domain for the path integral in the complex plane. We describe a family of such deformations, built using the holomorphic gradient flow, that interpolate between the original integration domain (where the sign problem is severe) and the union of relevant thimbles (where the sign problem is mild but a multimodal probability distribution complicates the Monte Carlo sampling). We show how this works in a fermionic model and for computing real time correlators for a simple thermal quantum field theory.
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12:00 to 12:30 |
Simon Catterall (Syracuse University, USA) |
Topology and Strong Four-fermion Interactions We study massless fermions interacting through a particular four-fermion term in four dimensions. Exact symmetries prevent the generation of bilinear fermion mass terms. We determine the structure of the low energy effective action for the auxiliary field needed to generate the four-fermion term and find it has a novel structure that admits topologically non-trivial defects with non-zero Hopf invariant. We show that fermions propagating in such a background pick up a mass without breaking symmetries. Furthermore, pairs of such defects experience a logarithmic interaction. We argue that a phase transition separates a phase where these defects proliferate from a broken phase where they are bound tightly. We conjecture that by tuning one additional operator the broken phase can be eliminated with a single BKT-like phase transition separating the massless from massive phases.
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12:30 to 14:00 |
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Lunch |
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14:00 to 14:30 |
Shailesh Chandrasekharan (Duke University, USA) |
Fermion Bag Approach to Hamiltonian Lattice Field Theory The Hamiltonian formulation of lattice Dirac fermions offers new opportunities to study strongly coupled quantum critical points in four-fermion models with enhanced symmetries. Unfortunately traditional quantum Monte Carlo methods to study these critical points encounter difficulties at large lattices sizes. Typical lattice sizes that are usually explored with exactly massless fermions are of the order of 600-1000 sites, with the largest sizes being of the order of 2500 sites. Going to larger sizes, while in principle possible, requires one to overcome numerical instabilities especially at low temperatures. We have recently extended the fermion bag idea to Hamiltonian methods and show that we can study lattice sizes of the order of 10000 sites without encountering any numerical instabilities. We have used this new approach to compute critical exponents in the 3D Gross-Neveu Ising model with one flavor of massless Dirac fermions using lattice sizes as large as 4096 sites.
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14:30 to 15:00 |
Ricardo Schiappa |
Resurgence and Transseries in String Theory I will give a brief overview of the uses and applications of resurgence and transseries within string theoretic contexts, with emphasis on topological and non-critical strings and their (matrix model) large N duals.
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15:00 to 15:30 |
Adi Armoni (Swansea University, UK) |
Holographic Corrections to the Veneziano Amplitude The celebrated Veneziano amplitude marks the birth of string theory. In this talk I will present a relation between large-N QCD and the Veneziano ampltiude. The derivation relies on the assumption of an area law, which is valid in flat space string theory, but not in real QCD. I will show how to incorporate effects due to holography that take into account deviations from an area law for small Wilson loops. Finally, I will also comment on the relation between the Veneziano amplitude and the lattice strong coupling expansion.
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15:30 to 16:00 |
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Tea |
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16:00 to 17:00 |
David Kaplan ( University of Washington, USA) |
Computing Reality (Infosys-ICTS Chandrasekhar Lectures) - Lecture 1 Physicists have beautiful theories for the microphysical interactions between particles, but face a number of problems when trying to compute predictions for the properties of matter. Many of these obstacles cannot be surmounted simply by using bigger computers and better code, but require the development of new theoretical insights. The speaker will discuss the particular examples from lattice quantum chromodynamics, including chiral symmetry and so-called sign problems, which lead us naturally to consider extra dimensions, topological insulators, and quantum computers.
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17:00 to 17:30 |
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High Tea |
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18:30 to 19:30 |
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Cultural Event |
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