Shuzhe Shi, Tsinghua
[QCD theory seminar] Real time non-perturbative dynamics in Schwinger model — jet production, charge transport, and more
Online (Zoom)
Addressing QCD scattering processes theoretically requires a real-time, nonperturbative method. It is well known that the Schwinger model [QED in (1+1) dimensions] shares many common properties with QCD, including confinement, chiral symmetry breaking, and the existence of vacuum fermion condensate. As a step in developing such an approach, we report here on fully quantum simulations, using classical devices, of a massive Schwinger model. We study the chiral condensate and entanglement entropy caused by jet propagation[2301.11991]. We also explore the propagation of vector and axial charge, i.e., CMW, and observe different oscillation frequencies[2305.05685]. The phase structure of the Schwinger model at finite temperature and chemical potential will also be discussed[2305.00996].
So Chigusa, LBNL & UC Berkeley
Estimating eV-Scale Background Rates for Dark Matter Direct Detection
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
A promising strategy for direct detection of sub-MeV dark matter is to look for phonon excitations in crystals. The crystal targets used in such experiments are typically not completely pure, and have impurities or defects. The point defects of our interest include the Frenkel defects, hydrogen and oxygen impurities, and so on. These defects can diffuse and recombine to emit energy in the form of phonons, and can potentially create a background for direct detection experiments. We estimate the defect densities produced through thermal excitations as well as radiogenic nuclear recoils. For various defect configurations, we quantify the diffusion and recombination rates for both thermal and quantum tunneling mechanisms. We find that the thermally generated Frenkel defects are effectively frozen at cryogenic temperatures and cannot diffuse to recombine with each other. The hydrogen impurity is the unique point defect that has non-negligible diffusion rate at cryogenic temperatures, and possibly contributes to the eV-scale events. The radiogenic defects produced on the surface can be annealed effectively at room temperature for typical defect configurations, but defects produced through radiogenic nuclear recoils in a shielded environment at cryogenic temperatures during the run-time of the experiment can recombine to produce eV-scale events. We provide estimates of these background event rates and give some remarks on subtleties we need to take care of in this kind of experimental setups.
Kunio Kaneta, Osaka University
Gravity at Work: Understanding Particle Production and Distribution
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
Despite its apparent weakness, gravity is a vital force driving particle production in the early Universe. To explore this production process, two different but well-established frameworks are commonly used, which are known as the Boltzmann and Bogoliubov approaches. I will first discuss a crucial aspect of these frameworks—their equivalence in pure gravitational production—to answer the question of whether these approaches yield consistent outcomes. In doing so, we will see the phase space distribution as a key quantity. This distribution will then serve as a useful tool to address yet another important question: Did the Higgs field predominantly exist as condensate or fluctuations in the earliest times? which will be discussed in the second part of the talk.
望月拓郎, 京都大学数理解析研究所
[金茶会] 代数・幾何・解析の不思議なつながり- 純ツイスター D-加群とその周辺
小林ホール リモート会場：J-PARC研究棟2階会議室 https://kds.kek.jp/event/46787/
https://kds.kek.jp/event/46787/
物理において見出された概念が, 数学にとりいれられた後, 元の状況から離れて独自の進化を遂げることがあります. 私が研究しているツイスターD加群もその一例です. この講演では, 物理に由来する概念が, 数学におけるどのような概念と結びついて, ツイスターD加群というものにいたったのか, ということを紹介したいと思っています.
Takashi Shimomura, Miyazaki University
Revisiting sterile neutrino dark matter in gauged B-L model
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
Sterile neutrino is a decaying dark matter candidate which can be produced non-thermally in the early Universe. Gauged B-L symmetric extension of the standard model naturally accommodates such a sterile neutrino dark matter, and also provides new mediators, B-L gauge boson and symmetry breaking scalar boson. Viable ranges of the dark matter mass and coupling have been studied in this mode. In this talk, we reexamine the freeze-in production of the sterile neutrino dark matter in gauged B-L model. Longitudinal mode contributions in scattering processes as well as inverse decays of the B-L gauge boson and scalar boson are taken into account in our analyses. We will discuss the contributions from these for different mass spectra of the dark matter, gauge boson and scalar boson. Then it is shown that the contributions from these are large and the allowed parameter space is changed from previous studies.
Avelino Vicente (IFIC, Valencia (Spain))
The Scotogenic mechanism: from model to paradigm
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom Neutrinos are very light fermions, a fact that can be well understood if their masses are induced at loop level. Many radiative neutrino mass models have been proposed along the years. The Scotogenic model is a very economical and popular setup that induces Majorana neutrino masses at the 1-loop level and includes a viable dark matter candidate. Based on the original model, many variants can be constructed.
Neutrinos are very light fermions, a fact that can be well understood if their masses are induced at loop level. Many radiative neutrino mass models have been proposed along the years. The Scotogenic model is a very economical and popular setup that induces Majorana neutrino masses at the 1-loop level and includes a viable dark matter candidate. Based on the original model, many variants can be constructed.
We discuss specific variations of the Scotogenic model with alternative representations under the Standard Model gauge group and additional Scotogenic states, perhaps coming from ultraviolet extended setups. These variants of the Scotogenic paradigm have novel phenomenological predictions and may explain some long-standing anomalies.
Zixia Wei, RIKEN iTHEMS
Low entanglement states, black holes and computational efficiency
Hybrid On-site: Seminar room, Kenkyu honkan 3F Online: Zoom
In modern statistical physics, typicality plays a crucial role since it states that almost all the microstates possessing a certain energy are locally indistinguishable from the canonical ensemble. Such states are called typical states and possess a large amount of entanglement. On the other hand, states whose entanglement are parameterically lower than a state are rare. We will call such states low entanglement states. In this talk, we will show that low entanglement states, while rare, are sufficient to account for the leading order of the thermodynamic entropy. We will also present a concrete way to construct such a basis. At the end, we will discuss its implication to the black holes, and its applications to computational physics.
Keisuke Harigaya, University of Chicago
Parity symmetry breaking scale and Standard Model parameters
Hybrid On-site: Seminar room, Kenkyu honkan 3F Online: Zoom
The strong CP problem can be solved by parity symmetry. We first review two classes of models: the ones with the minimal fermion content and the ones with the minimal Higgs content. We then focus on the latter class of models and show that the parity symmetry breaking scale is predicted to be the energy scale at which the standard model Higgs quartic coupling vanishes. Surprisingly, after fixing the parity symmetry breaking scale in this way, the gauge coupling constants unify at a high energy scale. We also discuss a model with a dark matter candidate and show that the dark matter direct detection rate is predicted as a function of the standard model parameters.
Zoltan Fodor, Pennsylvania State University
Tension for the anomalous magnetic moment of the muon: 4.2 sigma, indeed?
Hybrid On-site: Seminar room, Kenkyu honkan 3F Online: Zoom Twenty years ago, in an experiment at Brookhaven National Laboratory, physicists detected what seemed to be a discrepancy between measurements of the muon’s magnetic moment and theoretical calculations of what that measurement should be, raising the tantalizing possibility of physical particles or forces as yet undiscovered. The Fermilab team has announced that their precise measurement supports this possibility. The reported significance for new physics is 4.2 sigma just slightly below the discovory level of 5 sigma. However, an extensive new calculation of the muon’s magnetic moment using lattice QCD by the BMW-collaboration reduces the gap between theory and experimental measurements. In this talk both the theoretical and experimental aspects are summarized with two possible narratives:
Twenty years ago, in an experiment at Brookhaven National Laboratory, physicists detected what seemed to be a discrepancy between measurements of the muon’s magnetic moment and theoretical calculations of what that measurement should be, raising the tantalizing possibility of physical particles or forces as yet undiscovered. The Fermilab team has announced that their precise measurement supports this possibility. The reported significance for new physics is 4.2 sigma just slightly below the discovory level of 5 sigma. However, an extensive new calculation of the muon’s magnetic moment using lattice QCD by the BMW-collaboration reduces the gap between theory and experimental measurements. In this talk both the theoretical and experimental aspects are summarized with two possible narratives:
a) almost discovery or b) Standard Model re-inforced. Some details of the lattice caluculation are also shown.
Philip Lu, Seoul National University
Sterile Neutrinos and Primordial Black Holes: Dark Matter Candidates
Hybrid On-site: Seminar room, Kenkyu honkan 3F Online: Zoom
