SCHOOL OF PHYSICS :: Seminars

Seminars

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Tue Jun 11, 2024 (1403/3/22)

	Jun 11 1403/3/22	14:00	Probing Boosted Dark Matter through Small-Scale Astrophysical Structures Show Abstract Abstract:The cosmological data from a small-scale astrophysical structure and future gravitational wave (GW) experiments hold great promise in shedding light on the nature of dark matter (DM). First, we explore a two-component DM model with a sizable mass splitting and self-interaction for a light component. By delving into temperature evolution, density perturbation, and N-body simulation, we find that the annihilation of the heavier components to the lighter ones effectively endows the latter with warm DM-like behavior. It takes advantage of all the distinct features that warm DM offers without observational mass constraints on the warm DM masses. Second, we explore a black hole binary system in the presence of the DM and corresponding GW signals. The dense region of DM can lead to the dephasing of gravitational waveforms, which can be detected by upcoming experiments such as LISA. Lecturer(s): Jeong Han Kim From : Chungbuk National University Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue May 21, 2024 (1403/3/1)

	May 21 1403/3/1	14:00	The impact of massive neutrinos on the morphology of the Universe Show Abstract Abstract:The morphology of the cosmos provides valuable information about the structure of the cosmic web, which can be used for cosmological inferences. In this talk, I will discuss the capability of Persistent Homology (PH) as a morphological tool to investigate the impact of massive neutrinos on the Large-Scale Structure (LSS). PH naturally addresses the multi-scale topological characteristics of the LSS as a distribution of clusters, loops, and voids. Utilizing the Fisher forecast formalism, I will provide a quantitative assessment about the constraining power of some PH vectorizations to estimate the parameters of the $\nu \Lambda CDM$ model. Lecturer(s): Mohammad Jalali From : Shahid Beheshti University Research Group: HEPCO Group Weekly Seminar More Info. : Link
Wed May 15, 2024 (1403/2/26)

	May 15 1403/2/26	18:00	Investigation of the Heisenberg's Uncertainty Principle and the Entropy Uncertainty Relation Show Abstract Abstract:Quantum mechanics provided precise and accurate explanations for the experiments conducted at the end of the 19th century. This led to the rapid development of quantum mechanics between 1905 and 1923, capturing the scientific community's attention. At the Solvay Conference in 1927, Werner Heisenberg, a leading figure of the Copenhagen interpretation, presented the uncertainty principle within quantum mechanics. In this lecture, we will explore the significance of Heisenberg's uncertainty principle, discuss a fundamental problem in its original formulation, and introduce the entropy uncertainty relation as an alternative. Furthermore, we will investigate into quantum entanglement and quantum discord, highlighting their crucial roles in precisely determining entropy uncertainty relation. Lecturer(s): Shahriar Salimi From : University of Kurdistan Research Group: Physics Colloquium More Info. : Link
Tue May 07, 2024 (1403/2/18)

	May 07 1403/2/18	14:00	Flat Connections from Irregular Conformal Blocks Show Abstract Abstract:I will talk about Liouville conformal blocks with degenerate primaries and one operator in an irregular representation of the Virasoro algebra. Using an algebraic approach, we derive modified BPZ equations satisfied by such blocks and subsequently construct corresponding integral representations based on integration over non-compact Lefschetz cycles. The integral representations are then used to derive novel types of flat connections on the irregular conformal block bundle. Lecturer(s): Babak Haghighat From : Tsinghua University Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Apr 23, 2024 (1403/2/4)

	Apr 23 1403/2/4	14:00	General Quantum Mechanics; a program for the resolution of the main issues in quantum theory, as a reconciliation of classical mechanics over phase space, general relativity and quantum mechanics. Show Abstract Abstract:General relativity is over the configuration space and is a Lagrangian mechanics. While quantum mechanics is quantization of classical mechanics over phase space which is a Hamiltonian mechanics. Thus it is difficult to reconciliate these two theories. Therefore, we first reestablish general relativity over phase space of spacetime and then combine it with quantum mechanics and the result is a new mechanics called general quantum mechanics. In general relativity, the acceleration of a test particle is defined relative to the metric of spacetime while in classical mechanics over phase space the metric has no role in the acceleration. Also in classical mechanics over phase space the measurement of a given observable has no role in the acceleration of a test particle unlike quantum mechanics which obeys Born rule which states that how the measurement makes an impact on the acceleration of the test particle. We reconciliate general relativity with classical mechanics over phase space and quantum mechanics by defining the acceleration of a test particle over phase space relative to the metric of phase space and also relative to a given observable. In general quantum mechanics, we have an equation for the collapse phenomenon which is the counterpart of geodesic equation in general relativity. The collapse equation is a nonlinear modification of the linear SchrÃ¶dinger equation. We also have an equation for the metric of phase space which is the counterpart of the Einstein field equation and is obtained by the least action principle over an action functional which is similar to the Hilbert action for the Einstein field equation. Namely, the Lagrangian of the action is a new type of curvature different than the Riemann curvature. As a result, we have a proposal for the resolution of the measurement problem in quantum mechanics. Lecturer(s): Seyed Ebrahim Akrami Sanzigh From : Semnan University Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Apr 09, 2024 (1403/1/21)

	Apr 09 1403/1/21	14:00	Model Selection Approach and Tension Metrics in Cosmology Show Abstract Abstract:Cosmology is a field that deals with a vast amount of data, and it is crucial to ensure consistency and measure the tension between data sets. Tension indicates either discordance between data sets or a problem with the underlying model. One of the most famous examples of tension in cosmology is the Hubble tension, which is a 3.5Ï? discrepancy between supernovae and CMB data in estimating the age of the Universe. While alternative models have been introduced to resolve this tension, it is necessary to use tension metrics to verify if these data sets are still discordant or in agreement even in alternative models. Furthermore, the existence of different models means that one has to choose the best model among competing models that fits observational data. Nested Sampling, a recent computational algorithm, enables us to perform a model selection approach alongside quantifying tension between different data sets. In this talk, we will discuss the tension metric and the model selection approach in cosmology. Lecturer(s): Mohsen Khorasani From : School of Physics, IPM Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Apr 02, 2024 (1403/1/14)

	Apr 02 1403/1/14	14:00	Anthropic Carbon Emission And the footprint of HEPCO researchers on Earth Show Abstract Abstract:The atmospheric CO2 has reached unprecedented amounts and the impact of human activities on the current situation is undeniable. In this talk, I briefly explain the problem of atmospheric CO2 variation and introduce the main strategies to control our carbon footprint as a HEPCO researcher according to the Arxiv 2403.03308 Lecturer(s): Saeed Ansari Fard From : School of Physics, IPM Research Group: HEPCO Weekly Seminar Special Series More Info. : Link
Sat Mar 02, 2024 (1402/12/12)

	Mar 02 1402/12/12	14:00	Variational Quantum Algorithms: From Many-Body Simulation to Machine Learning Problems Show Abstract Abstract:Near-term quantum simulators suffer from various imperfections. A key question is whether such noisy quantum devices can outperform classical computers. Several demonstrations for quantum advantage have been achieved for sampling problems in superconducting and optical platforms. While these proof of principle experiments show the superiority of quantum computers, they do not offer an immediate practical advantage due to the limited practicality of sampling problems. Variational quantum algorithms are the most promising approach for achieving practical quantum advantage. These algorithms benefit from a hybrid combination of quantum devices and classical optimizers. In this seminar, we show two distinct applications for such algorithms, namely: (i) quantum simulation of many-body systems; and (ii) machine learning problems. In the former, we show how symmetries can be harnessed in optimizing circuit design [1] and be implemented experimentally in superconducting quantum simulators [2]. For the latter, a novel error-mitigation algorithm is presented which significantly enhances the performance of variational quantum algorithms for supervised machine learning problems [3]. References: [1] Symmetry enhanced variational quantum eigensolver C. Lyu, X. Xu, M.-H. Yung, A. Bayat, Quantum 7, 899 (2023) [2] Multi-Level Variational Spectroscopy using a Programmable Quantum Simulator Z. Han, et. al., Phys. Rev. Research 6, 013015 (2024) [3] Ensemble-learning variational shallow-circuit quantum classifiers Q. Li, Y. Huang, X. Hou, Y. Li, X. Wang, A. Bayat, Phys. Rev. Research 6, 013027 (2024) Lecturer(s): Abolfazl Bayat From : University of Electronic Science and Technology of China Research Group: QIS Biweekly Seminars More Info. : Link
Sat Feb 24, 2024 (1402/12/5)

	Feb 24 1402/12/5	14:00	Classical algorithm for simulating experimental Gaussian boson sampling Show Abstract Abstract: Classical algorithm for simulating experimental Gaussian boson sampling Changhun Oh, Minzhao Liu, Yuri Alexeev, Bill Fefferman, and Liang Jiang https://arxiv.org/abs/2306.03709 Lecturer(s): Fatemeh Tarighi Tabesh From : School of Physics, IPM Research Group: QIS Group Journal Club More Info. : Link
Tue Feb 20, 2024 (1402/12/1)

	Feb 20 1402/12/1	14:56	Late-time domain walls in cosmological simulations Show Abstract Abstract:The study of domain walls and topological defects has a rich history in cosmology and they provide a wide range of novel phenomenology to experimentally test them. The motivations that they have been studied under include seeding the initial overdensities for structure formation, driving inflation, seeding a stochastic gravitational wave background like the one in NANOGrav, and providing the skeleton for the formation of larger structures than you would expect in LCDM. They have furthermore been linked to resolutions of some of the late-time cosmological tensions. I will in this talk present the asymmetron dark energy model, that exhibits late-time cosmological domain walls, and our implementation of it in the cosmological N-body code gevolution. I present some details on the domain walls' dynamics, their GW emission, their effect on clustering, and some observational signatures. Lecturer(s): Ã?yvind Christiansen From : Institute for Theoretical Astrophysics (ITA), University of Oslo (UiO) Research Group: HEPCO Group Weekly Seminar More Info. : Link
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