14 OCT 2021
10:00 - 18:00

Workshop (online)
Oct 14 , 2021 from 10 to 18

13 OCT 2021
16:00 - 17:00

The technological and theoretical advances in the past decades have led to the reemergence of machine learning (ML) applications in physical sciences providing unprecedented opportunities to find efficient and accurate solutions to the most challenging problems in these disciplines. Finding the electronic structures of real-world materials is one of the prime examples of such problems in quantum chemistry and condensed matter physics as they will shape the fundamental understanding of dynamics and evolution of electronic and magnetic properties. In this talk, I will present a brief review of the current state of ML applications in material sciences and also share some of our projects in the field of quantum chemistry. As an example, we will consider a neural network (NN) representation for approximating the full configuration interaction (FCI) wave function. The configuration interaction approach is considered to be a highly accurate representation of the exact wave function, and, in principle, can capture both the static and dynamic correlation effects in many body quantum systems. However, the exponential growth of the Hilbert space dimension with the number of electrons basically diminishes the prospect of using the FCI method for many interesting quantum systems. It will be shown that the NN wave functions are highly compact and accurate representations of the exact electronic structures when tested in a benchmark set of molecular systems.


To join the seminar, please follow this link:

https://www.skyroom.online/ch/schoolofnanoscience/weeklyseminars

and log in as guest.

13 OCT 2021
11:00 - 12:00

Abstract: In the context of gauge/gravity duality, it is known that some information-theoretic quantities in a quantum field theory may have a simple geometric description in a dual gravitational theory and vice versa. The most famous example should be the (entanglement) entropy that is related to the area of a certain extremal surface in a higher dimensional theory of gravity. In this talk, I will briefly review this dictionary and focus on the concept of Entanglement Wedge Cross-Section and its dual descriptions as a measure of correlation in mixed states. In particular, I will argue how this quantity may describe the thermalization process of a conformal field theory after a global quench.


Indico: https://indico.particles.ipm.ir/indico/event/432
https://meet.google.com/zfx-datc-ocm

13 OCT 2021
15:30 - 17:30

I will discuss how the property of "largeness" of a field (introduced by Pop) can be used in the model theory of fields to help solve conjectures and questions about fields whose first order theory is stable or simple. This is a joint with Erik Walsberg.

https://us06web.zoom.us/j/87929792112?pwd=WWNnTkEwOFQwRDdOVXNaK1UzZHBFZz09
Meeting ID: 879 2979 2112
Passcode: 496589

13 OCT 2021
14:00 - 15:00

Abstract:
Much of our present understanding of wave-function localization in one spatial dimension is based on the original Anderson model on a one-dimensional lattice. The experimental simulation of this model using cold atoms, owing to the high degree of control over system parameters, has made possible the direct observation of localization of matter waves. In this talk, after giving an introduction to Anderson localization, I will present some new results on localization properties of this model with a general hopping matrix.


Date: Wednesday, October 13, 2021
Time: 14:00-15:00

To join the webinar, please follow this link:
https://www.skyroom.online/ch/schoolofphysics/condensed-matter-and-statistical-physics
and log in as guest.

Organized by: Condensed Matter and Statistical Physics Group, School of Physics (IPM)

Queries about this event should be addressed to Dr. A. Faridi at azadeh.faridi@ipm.ir

12 OCT 2021
16:30 - 18:00

Abstract:
By using complex-variable methods one can extend conventional Hermitian quantum theories into the complex domain. The result is a huge and exciting new class of non-Hermitian parity-time-symmetric (PT-symmetric) theories that still obey the fundamental laws of quantum mechanics. These new theories have remarkable physical properties, which are currently under intense study by theorists and experimentalists. Many theoretical predictions have been verified in recent beautiful laboratory experiments.


Date: Tuesday, October 12th
4:30 p.m (Tehran time) unusual time

Zoom. (click)
Meeting ID: 871 3111 8837
Passcode: 315821

12 OCT 2021
15:00 - 16:00

Abstract: A certain partition function (called the superconformal index) of the N=4 super-Yang-Mills theory seems to encode various interesting contributions to the euclidean path-integral of its bulk dual. These include euclidean Black Holes, orbifolds of euclidean Black Holes, and conjecturally also euclidean Black Lenses and their orbifolds.
( for participating in this event, please contact us: "particles@ipm.ir" )

12 OCT 2021
17:30 - 19:30

Let $f:Y \\rightarrow X$ be a finite covering map of complex algebraic varieties. The essential dimension of $f$ is the smallest integer $e$ such that, birationally, $f$ arises as the pullback of a covering $Y'\\rightarrow X'$ of dimension $e$, via a map $X \\rightarrow X'$. This invariant goes back to classical questions about reducing the number of parameters in a solution to a general $n$-th degree polynomial, and appeared in work of Kronecker and Klein on solutions of the quintic.

I will report on joint work with Benson Farb and Jesse Wolfson, where we introduce a new technique, using prismatic cohomology, to obtain lower bounds on the essential dimension of certain coverings. For example, we show that for an abelian variety $A$ of dimension $g$ the multiplication by $p$ map $A \\rightarrow A$ has essential dimension $g$ for almost all primes $p$.


Zoom link:

https://us06web.zoom.us/j/9086116889?pwd=WGRFOGZWZ1FOMXJrcWpJMWFqUFIvQT09

Meeting ID: 908 611 6889

Passcode: 362880

6 OCT 2021
15:30 - 17:30

Let $T$ be an $aleph_0$-categorical theory in first order logic, $M$ its countable model, and $G(T) = mathrm{Aut}(M)$ with the topology of pointwise convergence. A classical result, due to Coquand (and appearing in a paper by Ahlbrandt and Ziegler) asserts that two aleph0-categorical theories $T$ and $T'$ are bi-interpretable if and only if $G(T)$ and $G(T')$ are isomorphic as topological groups. Moreover, one can reconstruct from $G(T)$ a theory $T'$ that is bi-interpretable with $T$. I will discuss a generalisation of this result to arbitrary complete theories in a countable language, at the cost of replacing the topological group $G(T)$ with a topological groupoid. Time permitting, I will also discuss what happens in continuous logic : I. Coquand's result for $aleph_0$-categorical theories generlises to continuous logic (B.-Kaïchouh). II. The groupoid approach works under an additional hypothesis (which holds for all classical theories and all $aleph_0$-categorical theories, as well as for a few more). III. In the general case we may run into trouble when we try to choose witnesses (i.e., introduce Skolem functions, in some sense). Some very recent work (still in progress) may allow us to overcome this as well.

https://us06web.zoom.us/j/87929792112?pwd=WWNnTkEwOFQwRDdOVXNaK1UzZHBFZz09
Meeting ID: 879 2979 2112
Passcode: 496589

4 OCT 2021
11:00 - 12:00

Abstract: The chiral magnetic effect (CME) is a phenomenon in which an electric current is induced parallel to an external magnetic field in the presence of chiral asymmetry in a fermionic system. In this paper, we show that the electric current induced by the dynamics of a pseudo-scalar field which anomalously couples to electromagnetic fields can be interpreted as closely analogous to the CME. In particular, the velocity of the pseudo-scalar field, which is the phase of a complex scalar, indicates that the system carries a global U(1) number asymmetry as the source of the induced current. We demonstrate that an initial kick to the phase-field velocity and an anomalous coupling between the phase-field and gauge fields are naturally provided, in a set-up such as the Affleck-Dine mechanism. The resulting asymmetry carried by the Affleck-Dine field can give rise to instability in the (electro)magnetic field. Cosmological consequences of this mechanism are also investigated.


Based on
https://arxiv.org/abs/1905.06966
https://meet.google.com/kie-vfvh-yit

30 SEP 2021
15:30 - 17:00

Organized by: School of Cognitive Sciences
to receive the link to join online, please send email to theoretical.neurosci.ipm@gmail.com

Abstract:


Modern multi-channel recording devices offer the opportunity to untangle the coordination mechanisms of neural activity at a mesoscopic level. However, this requires novel multivariate analysis techniques that link the high-dimensional data with biophysically realistic models of network activity. We develop a methodology to generalize the analysis of spike-field coupling (SFC) to the multi-channel setting, while allowing interpretability of such coupling based on neural field models of network activity. SFC characterizes the relation between the spiking activity of individual neurons and field activity, reflecting mesoscopic network dynamics, and typically measured by Local Field Potentials (LFP). Although SFC approaches have been extensively applied, they were focused on quantifying coupling one pair at a time (between one unit and one LFP channel), thereby remaining largely blind to the population-level interactions that generate them. As a consequence, the rich spatiotemporal patterns of spikes and LFPs remained largely under-exploited, despite the insights into the underlying circuit dynamics they may provide.



We introduce "Generalized Phase Locking Analysis (GPLA)" that summarizes the spike-field coupling from multi-channel data by three interpretable quantities: LFP and spike vectors represent the dominant spatial distribution and relative phase shifts of neuronal ensemble and field activity in the recorded structure, while the generalized Phase Locking Value quantifies the strength of the coupling between these patterns.



Furthermore, we demonstrate the capability and interpretability of GPLA with various simulated and experimental datasets. First, GPLA’s performance is superior to univariate measures in the presence of large amounts of noise. Next, the application of GPLA on simulations of hippocampal sharp-wave-ripples (SWR) reveals various characteristics of hippocampal circuitry (e.g. communication flow from CA3 to CA1 during the SWR) with minimal prior knowledge. Finally, combining neural field simulations and GPLA applied on Utah array data recorded from anesthetized macaque reveals synchronized clusters of sites/neurons. This global pattern of synchronization PFC supports long-range excitatory horizontal connections and strong local recurrent inhibition as a plausible connectivity scheme of the recorded structure (ventrolateral Prefrontal Cortex), that has been partially verified experimentally.



Lastly, we address one of the challenges of statistical analysis of parallel spike trains by taking a step beyond bootstrapping methods. We exploit novel statistical frameworks, namely the random matrix theory, and provide an analytical significance test. This is of paramount importance given the increasing dimensionality of modern recording techniques, such as Neuropixel, that need computationally efficient statistical tests.



In summary, with GPLA, we can quantify, characterize, and statistically assess the interactions between population spiking activity and mesoscopic network dynamics.






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