Milad Delfan Azari, Waseda University
Physics of fast collective neutrino oscillations in core-collapse supernovae
Online (Zoom), indico page, slides (kek.jp only)
Neutrinos are highly populated inside the core of massive stars. They play an important role in the explosion mechanism of core-collapse supernovae. It is known that, almost all of the energy in the gravitational collapse is emitted in the form of neutrinos. They may change their identity through so-called fast flavor conversion induced by mutual forward scatterings. If this fast flavor conversion happens, it may have an impact on the dynamics of supernova explosions, since it may occur near the neutrino sphere. In this presentation, the latest results of our understanding of the neutrino fast flavor conversions in core-collapse supernovae will be reported.
Graham White, Kavli IPMU
Learning about cosmology using astrometry
Online (Zoom), indico page, slides (kek.jp only)
Gaia is observing the position and path of an enormous number of stars. Future experiments promise to do so for even more stars at high precision. If the light from such a star is traveling to us through a stochastic gravitational wave background, the apparent position of the star will be displaced by an amount essentially independent of the distance but dependent on the strength of the gravitational wave. Correlations in such shifts from many stars can be used to detect or constrain a gravitational wave background. The frequency range probed partially fills the gap between pulsar timing arrays and LISA. We explore the potential cosmological consequences of this by looking at phase transitions, topological defects and pbhs.
Zebin Qiu, University of Tokyo
[QCD theory Seminar] Magnetic effects in dense nuclear matter through Skyrme model
Online (Zoom)
Skyrme model is among the simplest extensions of chiral effective theory including anomaly. We investigate how an external magnetic field deforms the classical Skyrmion soliton structure while maintaining the topological winding. We further identify quantized Skyrmions as neutrons and protons, revealing a mass split between them induced by the magnetic field. More intriguing aspects arise when we annex multiple Skyrmions to form a crystal and realize the ¥pi^0 domain wall as a special class of solution. We establish the thermodynamics and phase diagram of different classes of Skyrme crystals, beneath which is the topological transmutation between ¥pi_3(S^3) and ¥pi_1(S^1).
Kazuya Yonekura, Tohoku University
Atiyah-Patodi-Singer index theorem from axial anomaly
Online (Zoom) https://kds.kek.jp/event/38462/
I will talk about a simple physical derivation of the so-called Atiyah-Patodi-Singer (APS) index theorem. The derivation is just a minor modification of Fujikawa’s argument for the axial U(1) anomaly once we we understand a physical interpretation of the APS boundary condition. It is based on my recent work with Shun K. Kobayashi https://arxiv.org/abs/2103.10654
Juan Carlos Vasquez, University of Massachusetts
Resurgence of the QCD Adler function
Online (Zoom) https://kds.kek.jp/event/38304/
We study the QCD Adler function in the energy region ≈ 0.7 − 2.5 GeV, in which the non perturbative effects become dominant. Our analysis is a renormalon-based evaluation using transseries within the resurgence of the Renormalization-Group-Equation and does not require the Operator-Product-Expansion.
Christophe Royon, University of Kansas
[EX and IPNS joint seminar] Measuring intact protons at the LHC: From the odderon discovery to the search for axion-like particles
Online (Zoom)
In the first part of the talk, we will describe the odderon discovery by the TOTEM and D0 experiments. The analysis compares the p pbar elastic cross section as measured by the D0 Collaboration at a center-of-mass energy of 1.96 TeV to that in pp collisions as measured by the TOTEM Collaboration at 2.76, 7, 8, and 13 TeV. The two data sets disagree at the 3.4 sigma level and thus provide evidence for the t-channel exchange of a colorless, C-odd gluonic compound, also known as the odderon. We combine these results with a TOTEM analysis of the same C-odd exchange based on the total cross section and the ratio of the real to imaginary parts of the forward elastic strong interaction scattering amplitude in pp scattering, leading to a combined significance larger than 5 sigma. In a second part of the talk, we will describe the perspective on the search for quartic anomalous couplings and axion-like particles using tagged protons in the final state, leading to sensitivities to beyond standard model physics that improve by 2 to 3 orders of magnitude on the coupling. We will finish by decribing briefly the ultra fast silicon detectors for timing measurements as well as for medical and cosmic ray physics applications.
Michal P. Heller, Max Planck Institute and NCBJ
[QCD theory Seminar] New results on convergence of hydrodynamic gradient expansion
Online (Zoom) Relativistic hydrodynamics, viewed as an effective field theory, is formulated in a derivative expansion. Studies of applicability of relativistic hydrodynamics in nuclear collisions at RHIC and LHC prompted 1302.0697 to explore convergence properties of this expansion. This and subsequent works showed that the Bjorken flow gives rise to a gradient expansion with a vanishing radius of convergence in all but a single studied quark-gluon plasma model. In my talk I will overview the current status of this field, as well as outline new developments on this topic that, for the first time, allow to make definite statements about the
Relativistic hydrodynamics, viewed as an effective field theory, is formulated in a derivative expansion. Studies of applicability of relativistic hydrodynamics in nuclear collisions at RHIC and LHC prompted 1302.0697 to explore convergence properties of this expansion. This and subsequent works showed that the Bjorken flow gives rise to a gradient expansion with a vanishing radius of convergence in all but a single studied quark-gluon plasma model. In my talk I will overview the current status of this field, as well as outline new developments on this topic that, for the first time, allow to make definite statements about the
convergence of hydrodynamic gradient expansion. New results follow from 2007.05524 and an ongoing work.
Tokiro Numasawa, University of Tokyo
Four coupled SYK models and Nearly AdS2 gravities: Phase Transitions in Traversable wormholes and in Bra-ket wormholes
Online (Zoom) https://kds.kek.jp/event/38340/ Wormholes are interesting and important objects in gravity.
Wormholes are interesting and important objects in gravity.
In particular, recently controllable examples of traversable wormholes are constructed.
To understand these wormholes better, we study the two traversable wormhole configurations through the study of four coupled SYK models and nearly AdS2 gravities.
In the SYK model side, we construct a model that couples two copies of two coupled SYK models.
In the nearly AdS2 gravity side, we entangle matter fields in two copies of traversable wormholes.
In both cases, the systems show first order phase transitions at zero temperature by changing couplings, which is understood as the exchange of traversable wormhole configurations.
In nearly AdS2 gravity cases, through the double wick rotation, traversable wormholes are interpreted as bra-ket wormholes, which gives a connection between bra and ket vectors.
In Lorentzian signature, these bra-ket wormholes lead to two closed universes that are entangled with each other as well as matter fields in the flat space without dynamical gravity.
We study the effect of projection or entangling operation for matters on flat spaces and they cause phase transitions in bra-ket wormholes, which leads to the pair annihilation of closed universes.
Using these bra-ket wormholes, we discuss the way to embed states in 2d holographic CFTs into Hilbert space of many 2d free fields.
David Tong, University of Cambridge
How to Give Chiral Fermions a Mass
Online (Zoom), slides (kek.jp only)
Chiral fermions have the property that their left-handed and right-handed components transform differently under some symmetry. Folklore suggests that it is impossible to give such fermions a mass without breaking this symmetry. I’ll show, through a number of examples, why this folklore is wrong. In particular, I’ll show how one generation of fermions in the Standard Model can get a mass without the need for a Higgs boson that breaks electroweak symmetry.
Jun'ya Kume, RESCEU / The University of Tokyo
The role of chiral gravitational anomaly in cosmology
Online (Zoom), indico page, slides (kek.jp only)
