19 JAN 2022
11:00 - 12:00

Abstract: The presence of the insertion devices (IDs) in a storage ring impacts the electron beam properties in different ways. Passing the electrons through the ID changes the betatron tunes, betatron amplitude function, and equilibrium parameters like emittance and energy spreads. The expression of equilibrium parameters in terms of radiation integrals is a common method for computing the effect of IDs on beam parameters. The effect of coupling is not included in the radiation integral method, so it is expected that in the case of using elliptically polarized undulators or modeling the real lattice with errors, this method could not express the beam parameters precisely. On the other hand, the equilibrium distribution of the electron beam and its related parameters could be determined directly by the envelope method. The envelope formalism is the most accurate method to compute the beam properties. By studying the effect of IDs and lattice errors on beam parameters with both radiation integral and envelope methods, it could be shown that the envelope method could project the effect of magnetic imperfection and induced coupling from IDs on beam parameters.


Meeting Link

Indico: https://indico.particles.ipm.ir/indico/event/458/
https://meet.google.com/nix-qyya-atr

19 JAN 2022
13:30 - 15:00

In this talk, I present an overview of an updated version of the L-Galaxies semi-analytical model of galaxy formation and evolution based on Ayromlou et al. (2019, 2021b). I first describe the standard theory of galaxy formation and evolution and explain different kinds of galaxy formation modeling, including semi-analytical models and hydrodynamical simulations. I then introduce a local background environment (LBE) estimator to quantify environment locally for all galaxies within cosmological simulations. I use the time-evolving local environment of galaxies to develop a method to better account for environmental processes (e.g. ram-pressure stripping) within the Munich semi-analytical model of galaxy formation, L-Galaxies. I recalibrate the updated model using a Markov Chain Monte Carlo (MCMC) method and a few observational constraints. By comparing our results to data on galaxy properties in different environments from different surveys (e.g. SDSS, HSC), I demonstrate that the updated model significantly improves the agreement with the observations. Overall, in the vicinity of massive dark matter haloes, the new model produces stronger environmental dependencies, better recovering observed trends with halocentric distance up to several virial radii (several Megaparsecs). This is likely to influence the correlations between galaxies up to tens of Megaparsecs.

19 JAN 2022
14:00 - 15:00

Abstract:
This is talk about the dynamics of the generalized Rosenzweig-Porter model, which is known to possess three distinct phases: ergodic, multifractal and localized phases. Our focus is on the survival probability R(t), the probability of finding the initial state after time t . In particular, if the system is initially prepared in a highly-excited non-stationary state (wave packet) confined in space and containing a fixed fraction of all eigenstates, we show that R(t) can be used as a dynamical indicator to distinguish these three phases. Three main aspects are identified in different phases. The ergodic phase is characterized by the standard power-law decay of R(t) with periodic oscillations in time, surviving in the thermodynamic limit, with frequency equals to the energy bandwidth of the wave packet. In multifractal extended phase the survival probability shows an exponential decay but the decay rate vanishes in the thermodynamic limit in a non-trivial manner determined by the fractal dimension of wave functions. Localized phase is characterized by the saturation value of R(t →∞)=k, finite in the thermodynamic limit N→∞ , which approaches k=R(t →0) in this limit.


Date: Wednesday, January 19, 2022

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

18 JAN 2022
14:00 - 15:00

Date and time
Tuesday, 18th of January, 2022 (28th of Dey, 1400), 2:00 pm (Tehran zone)

Link
https://us02web.zoom.us/j/86984492174?pwd=QmozNTlZRnJLb3pKb0lpNlhwSjFwQT09

Meeting ID: 869 8449 2174
Passcode: 662580

Abstract
We assume that the points in volumes smaller than an elementary volume (which may have a Planck size) are indistinguishable in any physical experiment. This naturally leads to a picture of a discrete space with a finite number of degrees of freedom per elementary volume. In such discrete spaces, each elementary cell is completely characterized by displacement operators connecting a cell to the neighboring cells and by the spin connection. We define the torsion and curvature of the discrete spaces and show that in the limiting case of vanishing elementary volume the standard results for the continuous curved differentiable manifolds are completely reproduced.

18 JAN 2022
17:00 - 18:00

Abstract: n this talk, we present novel rigorous bounds on maximal volume slices in asymptotically AdS spacetimes. Under the Complexity=Volume conjecture, these results imply that the CFT vacuum is the simplest state, provided we assume the weak energy condition and no compact bulk dimensions. Next, we show that compact dimensions or tachyonic scalar fields can violate our result, giving rise to distinct effects that should be reproduced by any proposed dual to maximal volumes. Finally, we present a speed limit on the growth of volumes in terms of spacetime mass, which under the CV conjecture constitutes a holographic proof of Lloyd's bound for a class of spacetimes.
(for participating in this event, please contact us: "particles@ipm.ir" )

17 JAN 2022
11:00 - 12:00

Abstract: The role of off-shell terms in BDNK hydrodynamics is discussed.
Then an outline of the emergence of such terms from kinetic theory is presented.



Based on
https://arxiv.org/abs/2112.14042


Meeting Link
https://meet.google.com/zqd-hysu-beu

13 JAN 2022
11:00 - 12:00

The novel coronavirus that has been detected in China since January 7, 2020, has spread at an unprecedented rate to all countries around the world. In this lecture, we take a look at combinatorial models of epidemics that model how viruses spread among living organisms by mathematics and specifically graph theory; and then go over the biological results of the corresponding simulations on the impact of quarantine and social distancing. In this regard, we will discuss a very important random process in discrete mathematics called random walk, and after modeling daily urban transportation in different scenarios by graphs, the implications of this theory in these cases will be analyzed.

12 JAN 2022
17:00 - 18:30

I will discuss the validity of Extended Effective Field Theory of Inflation (EEFToI) in the regime where initial conditions are set with dispersion relations (w^2 proportional to k^6). After reviewing the power spectrum for some interesting corners of the parameter space, we will take a closer look at the strong coupling constraints and calculate the size of the non-Gaussianities in those regions of parameter space. I will also present our result for the shape of triangles that contribute to the enhancement of non-Gaussianities in this regime. We have found that there are allowed parts of parameter spaces where EEFToI description with initial conditions set with (w^2 proportional to k^6) is sensible and interesting.

12 JAN 2022
14:00 - 15:00

Tunability of the Casimir interaction has always been a challenging issue, especially in small-scale applications. Different mechanisms have recently been proposed to control the Casimir force between solid substrates through the manipulation of material properties using external stimuli such as temperature, external fields, and optical excitations. We show that the unique properties of ferrofluids (colloidal suspensions of superparamagnetic nanoparticles in a nonmagnetic host liquid) provide robust routes for the control of the Casimir interaction between solid (specifically, gold and glass) substrates separated by a thin ferrofluid layer. The tunability here arises due to the self-assembly of suspended magnetic nanoparticles into short magnetic chains; a reversible effect pertinent to equilibrium phases of semidilute ferrofluids subjected to external static magnetic fields, as observed in simulations and experiments. The chain formation makes the ferrofluid an anisotropic medium in its response to electromagnetic field fluctuations that produce the Casimir interaction between the bounding surfaces. Our calculations based on the Lifshitz formalism show that the resulting Casimir force can suitably be varied in magnitude and sign by adjusting the ambient temperature, strength and direction of an externally applied magnetic field, and volume fraction of the constituent nanoparticles.


To join the webinar, please follow this link and log in as a guest:


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

12 JAN 2022
14:00 - 15:00



https://us06web.zoom.us/j/86917547255
Meeting ID: 869 1754 7255

11 JAN 2022
14:00 - 15:00

Observation of high energy cosmic neutrinos by ICECUBE has ushered in a new era in exploring both cosmos and new physics beyond the Standard Model (SM). In the standard picture, although mostly $\nu_\mu$ and $\nu_e$ are produced in the source, oscillation will produce $\nu_\tau\;en\; route$. Certain beyond SM scenarios, like interaction with



ultralight DM can alter this picture. Thus, the flavor composition of the cosmic neutrino flux can open up the possibility of exploring certain beyond the SM scenarios that are inaccessible otherwise. We show that the $\tau$ flavor holds a special place among the neutrino flavors in elucidating new physics. Interpreting the two anomalous events observed by ANITA as $\nu_\tau$ events makes the $\tau$ flavor even more intriguing. We study how the detection of the two tau events by ICECUBE constrains the interaction of the neutrinos with ultralight dark matter and discuss the implications of this interaction for even higher energy cosmic neutrinos detectable by future radio telescopes such as ARA, ARIANNA, and GRAND. We also revisit the 3+1 neutrino scheme as a solution to the two anomalous ANITA events and clarify a misconception that exists in the literature about the evolution of high energy neutrinos in matter within the 3+1 scheme with a possibility of scattering off nuclei. We show that the existing bounds on the flux of $\nu_\tau$ with the energy of EeV rule out this solution for the ANITA events. We show that the 3+1 solution can be saved from both this bound and from the bound on the extra relativistic degrees of freedom in the early universe by turning on the interaction of neutrinos with ultralight dark matter.



Meeting ID: 869 8449 2174


Passcode: 662580

10 JAN 2022
11:00 - 12:00

Abstract: In this study, we consider three dark energy models in which $\Lambda$ is not constant, but has a dynamic nature that depends on the Hubble parameter $H$ and/or its time derivative $\dot{H}$.
We analyze the generalized running vacuum model, for which $\Lambda(H)=A+BH^2+C\dot{H}$, along with the two models obtained by setting $B$ or $C$ equal to zero. A null value for $C$ yields the classical running vacuum model (RVM), while $B=0$ corresponds to what we term the generalized running vacuum sub-case, or GRVS. Our main aim is to investigate whether these models can accommodate non-zero spatial curvature. To this end, we carry out a Markov Chain Monte Carlo analysis using data for the observables associated with Type-Ia supernovae, cosmic chronometers, the cosmic microwave background and baryon acoustic oscillations, as well as two values for the Hubble constant. Then we include data relating to the growth of large-scale structure (LSS) and repeat the procedure. Our results indicate that taking LSS observations into account helps to tighten constraints and determine a definite sign for the model parameters. In the case of the RVM and GRVS, the addition of growth data results in dynamical
vacuum energy being preferred to a cosmological constant at a little over $1\sigma$. This happens in both the flat and non-flat scenarios -- there are only a few exceptions -- but comes at the cost of an extra parameter which can degrade the performance of the models (as assessed by model selection criteria). Of special relevance is the fact that the inclusion of LSS data appears to increase compatibility with a flat geometry. It also brings the constraints on the Hubble constant closer to the range of values
established by Planck.



Based on
https://arxiv.org/abs/1812.02790

Meeting Link
meet.google.com/esj-ogws-teb