سخنران: ابوالفضل میرجلیلی، دانشگاه یزد

30 دی 1399
11:00 تا 12:00


تصحیحات جرمی بر معادله های تحول
DGLAP

سخنران: مهرداد میربابایی
مرکز بین المللی فیزیک نظری

30 دی 1399
13:30 تا 15:00

ین سمینار روز چهارشنبه۱ بهمن ماه ساعت 13:30 به صورت آنلاین برگزار می شود.

سخنران: H. Rostami, KTH Royal Institute of Technology and Stockholm University

30 دی 1399
14:00 تا 15:00

Abstract:

Because of the many-body interactions, the standard concepts of nonlinear response to electromagnetic fields break down in two dimensional Dirac systems, like graphene, in the quantum regime close to the Dirac point. I this talk, I will first discuss the dramatic impact of long-range Coulomb interaction on the nonlinear optical responses owing to the plasmonic and screening effects [1]. Then, I will present how using a conserving Baym-Kadanoff approach, we can provide a fully compelling theory of nonlinear optical and transport response of a Dirac system to electric fields in the presence of disorder scattering. We show that the nonlinear terms are strikingly ruled by the appearance of a dominant two-photon vertex which is absent at the bare level and finite even in the weak-coupling limit. Such two-photon vertex self-generation [2] highlights the crucial role of the frequency and field dependence of the scattering rates in the nonlinear regime. Moreover, we surprisingly predict four- and five-photon incoherent features in the third order optical response of the system [3]. Our study reveals a novel many-body mechanism in the nonlinear response of Dirac materials whose effects are predicted to be observable in nonlinear dc transport, terahertz third-harmonic generation, and the second-order difference-frequency response of graphene.

[1] H. Rostami, M.I. Katsnelson, and M. Polini, PRB 95, 035416 (2017).
[2] H. Rostami and E. Cappelluti, arXiv:2007.08282 (2020).
[3] H. Rostami and E. Cappelluti, arXiv:2011.03824 (2020).


Date: Wednesday, January 20, 2021 / چهارشنبه، ۱ بهمن ۱۳۹۹

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

سخنران: لارنت لافرج, آی اچ ای اس، فرانسه

30 دی 1399
16:30 تا 18:00

The ancient Greek word "geometry" is, with its etymological meaning of "measurement of the earth", one of the oldest of mathematics. The discovery of non-euclidean geometries in the 19th century dramatically increased the scope of geometry. This scope was further extended in the 20th century by dividing geometry into branches differing in their objects of study and their methods: topology, differential geometry, Riemannian geometry, symplectic geometry, complex geometry, algebraic geometry, ... Grothendieck is known primarily for having re-founded algebraic geometry on entirely new bases. But he himself considered himself to be a general mathematician, not a specialist. So one may wonder whether the word "geometry", which he used very often without ever defining it, has for him a precise meaning that goes beyond algebraic geometry, and whether certain notions he introduced or to which he gave a central role are likely to apply to everything that one might imagine to be called geometric. The aim of the presentation will be to propose elements of an answer to this question.

To get more information about the colloquium, join to the following google group:
https://groups.google.com/g/ipm-math-colloquium

سخنران: کریستین لمپ, دانشگاه پورتو، پرتقال

2 بهمن 1399
11:00 تا 13:00

Shortly after Eckmann and Schopf's definition of the concept of an injective modules, Matlis showed that the injective hull of a simple module over a commutative Noetherian ring R is Artinian. Vamos showed that the latter condition is actually equivalent to the commutative ring R being locally Noetherian. However, injective hulls of simple modules over non-commutative Noetherian rings might not be Artinian. Slightly different, but related, one might consider Noetherian algebras A over a field F and ask whether any finitely generated submodule of the injective hull of a finite dimensional simple A-module need to be finite dimensional. In other words, is the category of locally finite dimensional representations of A closed under taking injective hulls. This is certainly the case for commutative algebras, but not for non-commutative algebras. Feldvoss proved, using results of Donkin and Dahlberg, that the category of locally finite dimensional representations over an enveloping algebra $U(g)$ of a finite dimensional Lie algebra $g$ is closed under taking injective hulls if and only if $g$ is a solvable Lie algebra. Furthermore, the group ring $F[G]$ of a polycyclic-by-finite group also has this property. Having these motivating examples in mind we intend to find necessary and sufficient conditions for the category of locally finite dimensional representations over a Noetherian algebra A over a field F to be closed under taking injective hulls.

In the first talk we will characterize Noetherian algebras A whose category of locally finite dimensional representations is essentially closed through their finite dual coalgebra
$$A^circ = {f in Hom(A,F): mathrm{Ker}(f) mbox{ contains an ideal of finite codimension}}$$ and provide sufficient conditions that involve the maximal ideals of A of finite codimension. We then consider Ore extensions of an algebra A, which are non-commutative polynomial rings in a variable x such that the coefficients in A obey to $$xa = sigma(a)x+delta(a) , qquad forall a in A$$ for a given automorphism $sigma$ and a $sigma$-derivation $delta$ of $A$. As an important tool we will use the Rees ring of an ideal in the Ore extension and find condition under which it is Noetherian.

In the second talk we will provide some background on the theory of Hopf algebras, having in mind that enveloping algebras of Lie algebras and group algebras are fundamental example. We will show that the question of the category of locally finite dimensional representations of a Noetherian Hopf algebra to be essentially closed can be reduced to the study of finitely generated extensions of the trivial representation. Our main results will show that Ore extension of commutative Noetherian Hopf algebras, certain Hopf crossed product algebra $A#_sigma H$ and all affine Hopf algebra domains of Gelfand-Kirillov dimension $leq 2$ with $Ext_H^1(F,F)
eq 0$ are Noetherian algebras whose category of locally finite representations is essentially closed.

Throughout the talks we will assume that the base field is algebraically closed and has characteristic zero.

The talks will be based on the preprint ``Locally Finite Representations Over Noetherian Hopf algebras" jointly written with my coauthor Can Hatipoglu. A PDF of this preprint can be found on ArXiv: href{https://arxiv.org/abs/2010.14192}{ exttt{https://arxiv.org/abs/2010.14192}}





Access link:


https://meet.google.com/ndk-abim-gxy

سخنران: پژوهشکده ذرات و شتابگرها

2 بهمن 1399
11:00 تا 12:00

ژورنال کلاب

سخنران: دکتر صدرا ساده، دپارتمان مهندسی پزشکی، امپریال کالج لندن

8 بهمن 1399
16:00 تا 17:30

ژورنال کلاب علوم اعصاب نظری

برای دریافت پیوند عضویت آنلاین ، لطفاً با theoretical.neurosci.ipm@gmail.com تماس بگیرید.
چکیده:

شبکه‌های نورونی در مغز متشکل از تعداد زیادی نورون و تعداد بیشتری اتصال میان آن‌ها است. چالش جدی پیش روی علوم اعصاب فهم و تحلیل این است که چگونه این مدارهای پیچیده نورونی در ارتباط با یکدیگر کار می‌کنند، و از این طریق به کارکردهای مختلف حسی و شناختی می‌انجامند. یک شیوه موثر برای تحلیل بهتر این شبکه‌های نورونی تحریک اختلالی آن‌ها است: با ایجاد تغییرِ اندکی در میزان فعالیت نورون‌ها در شرایط طبیعی کارکردشان، اثر این اختلال بر فعالیت باقی نورون‌ها در شبکه و نهایتا تغییر رفتار سنجیده می‌شود. در سال‌های اخیر، تکنیک‌های جدید به خصوص امکان اندازه‌گیری و تحریک هم‌زمان توسط اپتوژنتیک، امکان استفاده از این رویکرد برای فهم کارکردی و محاسباتی مغز را به مراتب تسهیل کرده است. استفاده راهگشا از این تکنیک‌ها اما نیازمند فهم محاسباتی از اثر آن‌ها و در نهایت، توانایی ارائه مدل برای ارتباط آن‌ها به اتصال‌های نورونی، دینامیک تحول شبکه‌ای و کارکردهای مغزی است. این ارائه به بررسی جنبه‌های محاسباتی این تحلیل اختلالی و برخی مدل‌های مربوط برای فهم آن می‌پردازد.



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سخنران: ابوالفضل تذری

8 بهمن 1399
13:00 تا 17:00

کارگاه آنلاین شبکه عصبی


چهارشنبه 8 بهمن 1399 ساعت 13 الی 17