16 SEP 2020
11:00 - 12:00

Abstract: Our main aim in this paper is to constrain the effective field theory describing the top quark couplings through the e−e+→tt~+jet process. The analysis is carried out considering two different center-of-mass energies of 500 and 3000 GeV including a realistic simulation of the detector response and the main sources of background processes. The expected limits at 95% CL are derived on the new physics couplings such as tt~gamma, tt~Z, and tt~g for each benchmark scenario using the dileptonic tt~ final state. We show that the 95% CL limits on dimensionless Wilson coefficients considered in this analysis could be probed down to 10−4.




https://www.skyroom.online/ch/ipm-particles/school-of-particles-and-accelerators-weekly-meeting


Indico: https://indico.particles.ipm.ir/indico/event/379

16 SEP 2020
15:30 - 17:30

We show that (assuming large cardinals) set theory is a tractable (and we dare to say tame) first order theory when formalized in a first order signature with natural predicate symbols for the basic definable concepts of second and third order arithmetic, and appealing to the model-theoretic notions of model completeness and model companionship. Specifically we develop a general framework linking generic absoluteness results to model companionship and show that (with the required care in details) a $Pi_2$-property formalized in an appropriate language for second or third order number theory is forcible from some T extending ZFC + large cardinals if and only if it is consistent with the universal fragment of T if and only if it is realized in the model companion of T.
Part (but not all) of our results are conditional to the proof of Schindler and Aspero that Woodin's axiom* can be forced by a stationary set preserving forcing.
Please send an email to r.zoghi@gmail.com to join this lecture.

16 SEP 2020
14:00 - 15:00

Abstract:

A driven fan that spins to create a flow of air would conversely rotate, if we turn it off, and subject it to a strong external flow. This is a classic example of reciprocity between cause and effect, in a life scale experiment. In small scale hydrodynamics, however, when the Reynolds number is quite low, a swimmer (pump) would generate a net motion (flow) only if its constructing parts non-trivially follow a pattern of motion which breaks time reciprocity. Here, considering a simple and well-controlled system of two micron-sized beads, we investigate if the mentioned exchange of physical cause and effect also holds at the low Reynolds number situations. Two suspending microbeads, each held by an optical trap, are subjected to an external fluid flow. Apart from their local fluctuations, the two beads interact with each other through hydrodynamic interactions. We successfully verify that the external flow, causes the two beads to imitate the very motion they had when intended to produce a net fluid flow. Extending this exploration to a chain of many beads, i.e. a flexible polymer, we successfully confirm that the aforementioned reciprocity in physical causes and effect even for a more complicated system, like a polymer chain. Finally, we observe that the onset of external flow results in a non-trivial flow of heat along the chain! The coupling between fluid flow and the heat flow, leads us to investigate if Onsager’s reciprocal relations also hold for such a system of suspending beads/polymer in an external fluid flow.



Date: Wednesday, September 16, 2020

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)

16 SEP 2020
16:00 - 19:00

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15 SEP 2020
14:00 - 15:00

Abstract:
In this talk, I report on a new method for obtaining a solution to the sourced Maxwell equations in Kerr in a radiation gauge. The basic structure of the solution consists of a "reconstructed part", which is given in terms of a Hertz potential, and a "corrector". The Hertz potential is a solution to a suitable Teukolsky equation.
As we demonstrate, unlike in vacuum, the corrector is in general necessary, but it can be obtained by integrating a simple transport equation. Thus, our method can be seen as a generalization of the well-known Cohen-Kegeles-Chzarnowski method to the case of source, which has been a long standing and unsolved problem.


Date: Tuesday, 8 September
2 p.m. - 3 p.m.

Skyroom Link: https://www.skyroom.online/ch/schoolofphysics/hepco-group


Skype link for emergency:
https://join.skype.com/cm7iyEUWJVCf

15 SEP 2020
16:00 - 18:00

Abstract: Heavy-ion collisions create strong fluid vorticity in the produced quark-gluon matter. Such fluid vorticity polarizes the spin of the constituent particles and leads to the 'spin polarization' observables of hadrons. I will discuss the mechanisms of the generation of fluid vorticity and some interesting properties of vorticities. I will then discuss how the global spin-polarization observable is understood in terms of vorticity. The local spin polarization is, however, not yet understood. I will talk about some theoretical progress that may shine a light on understanding the local spin polarization in heavy-ion collisions

15 SEP 2020
16:30 - 18:30

In this presentation, we start with some results about closed geodesics' growth rate in various cases (including geodesics on manifolds with negative sectional curvatures) and the similarity of some of them with prime number theorem. After that, we introduce the marked length spectrum function. An important conjecture says this function identifies the metric of a closed negatively curved manifold.

To get the access link, register at
https://forms.gle/3AbXZeCucKWCuumR7
by the day before the event.

[ICMC-IMPA-IPM Joint Mathemaics Seminars]

14 SEP 2020
11:00 - 12:00

Based on 2009.00014 [hep-ph]


Abstract: We present an improved determination of the strange quark and anti-quark parton distribution functions of the proton by means of a global QCD analysis that takes into account a comprehensive set of strangeness-sensitive measurements: charm-tagged cross sections for fixed-target neutrino-nucleus deep-inelastic scattering, and cross sections for inclusive gauge-boson production and W-boson production in association with light jets or charm quarks at hadron colliders. Our analysis is accurate to next-to-next-to leading order in perturbative QCD and specifically includes charm-quark mass corrections to neutrino-nucleus structure functions. We find that a good overall description of the input dataset can be achieved and that a strangeness moderately suppressed in comparison to the rest of the light sea quarks is strongly favored by the global analysis.


https://www.skyroom.online/ch/ipm-particles/journal-club-ep

14 SEP 2020
14:00 - 17:00


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9 SEP 2020
16:00 - 17:30

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

Abstract:


Spike-timing-dependent plasticity (STDP) is a fundamental mechanism that modifies synaptic strengths based on the relative timing of pre- and postsynaptic spikes. However, taking into account the propagation delays may affect the temporal order of spikes. In this way, qualitatively different connectivity patterns can emerge between neurons. In particular, we show that for a system of two coupled neurons, strong bidirectional synapses can be preserved and potentiated or a simultaneously decoupled state can emerge. Intriguingly, this finding also translates to large networks of neurons and, hence, crucially impacts on the overall hierarchical connectivity patterns of oscillatory neuronal networks. Furthermore, the presence of delay- and STDP-induced bistability provides a suitable opportunity for optimizing decoupling brain stimulation patterns (e.g. in the treatment of Parkinson’s disease) aimed at shifting the dynamics of the diseased brain towards healthy attractor states.



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