Mattia Bruno, CERN
New perspectives on Amplitudes from Eucliean Correlators
Online (Zoom)
The Monte Carlo methods used in Lattice QCD simulations rely on the rotation of the path integral to Euclidean metric. Unfortunately, the limited knowledge of correlation functions on finite subsets of points prevents a direct analytic continuation to Minkowski signature. In their seminal publication of 1990, Maiani and Testa showed that physical amplitudes away from threshold cannot be directly extracted, ie without an inverse problem, from Euclidean correlators, due to off-shell contaminations. In this presentation, I revisit and extend their original work, and explore the connection with recent developments on the inverse problem in Lattice QCD.
Shan-Ming Ruan, YITP Kyoto University
On the Page curve under final state projection
Online (Zoom) https://kds.kek.jp/event/40712/
The black hole singularity plays a crucial role in formulating Hawking’s information paradox. The global spacetime analysis may be reconciled with unitarity by imposing a final state boundary condition on the spacelike singularity. Motivated by the final state proposal, we explore the effect on final state projection in two-dimensional conformal field theories in our recent paper arXiv:2112.08433. We calculate the time evolution under postselection by employing the real part of pseudo-entropy to estimate the amount of quantum entanglement averaged over histories between the initial and final states. We find that this quantity possesses a Page curve-like behavior.
Paul Lasky, Monash University
[JpDe Joint Seminar] What's next in gravitational-wave astronomy?
Online external homepage
The LIGO and Virgo interferometers have observed almost 100 gravitational-wave signals from collisions of black holes and neutron stars. Meanwhile, pulsar timing arrays around the globe are beginning to see interesting signals that may be attributed to a gravitational-wave stochastic background, potentially from supermassive black hole binaries throughout the Universe, or even primordial gravitational waves from the very early Universe. In this talk, I will review the state of both ground-based gravitational-wave astronomy and pulsar timing arrays. I will also discuss our ability to use current and future gravitational-wave observations to test Einstein’s general theory of relativity in the ultra-strong field regime.
Yasuaki Hikida, YITP Kyoto University
dS_3/CFT_2 correspondence
Online (Zoom) https://kds.kek.jp/event/40653/
In order to understand quantum gravity on cosmological backgrounds, dS/CFT correspondence is expected to play important roles. However, it has not been well understood yet compared with AdS/CFT correspondence. One of the reasons is that currently very few concrete examples are available and only generic arguments can be made. Recently, we provided a concrete proposal of dS_3/CFT_2 correspondence by making use of Chern-Simons description of (higher spin) gravity. In this talk, we will explain our proposal and supporting arguments by examining partition functions, correlation functions and so on.
Hiromasa Takaura, KEK theory center
[EX] μTRISTAN
Online (Zoom) We recently proposed new collider experiments using a μ+ beam, utilizing the technology developed for the muon g-2 experiment at J-PARC to realize low emittance. We consider the experiment where the μ+ beam accelerated to 1 TeV collides with the TRISTAN energy (30 GeV) electron beam in the storage ring with the circumference of 3 km, the same size as the TRISTAN ring. The center-of-mass energy amounts to √s=346 GeV. Estimating possible luminosity, we find that the μ+e- collider can be a good Higgs boson factory and precision measurements of Higgs couplings are possible. We also consider a μ+μ+ collider with center-of-mass energy √s=2 TeV using the same ring. As a first study of new physics search, we discuss SUSY particle production processes in these colliders.
We recently proposed new collider experiments using a μ+ beam, utilizing the technology developed for the muon g-2 experiment at J-PARC to realize low emittance. We consider the experiment where the μ+ beam accelerated to 1 TeV collides with the TRISTAN energy (30 GeV) electron beam in the storage ring with the circumference of 3 km, the same size as the TRISTAN ring. The center-of-mass energy amounts to √s=346 GeV. Estimating possible luminosity, we find that the μ+e- collider can be a good Higgs boson factory and precision measurements of Higgs couplings are possible. We also consider a μ+μ+ collider with center-of-mass energy √s=2 TeV using the same ring. As a first study of new physics search, we discuss SUSY particle production processes in these colliders.
Reference:
arXiv: 2201.06664
Y. Hamada, R. Kitano, R. Matsudo, H. Takaura, M. Yoshida
Masaki Oshikawa, ISSP University of Tokyo
Resolving the Berezinskii-Kosterlitz-Thouless transition in the two-dimensional XY model with tensor-network-based level spectroscopy
Online (Zoom) https://kds.kek.jp/event/41067/
The Berezinskii-Kosterlitz-Thouless (BKT) transition was historically the first example of topological phase transitions. Here we re-investigate the BKT transition in the 2D classical XY model, combining the Tensor Network Renormalization (TNR) and the Level Spectroscopy method based on the finite-size scaling of the Conformal Field Theory. By systematically analyzing the spectrum of the transfer matrix of the systems of various moderate sizes which can be accurately handled with a finite bond dimension, we determine the critical point removing the logarithmic corrections. This improves the accuracy by an order of magnitude over previous studies including those utilizing TNR. Our analysis also gives a visualization of the celebrated Kosterlitz Renormalization Group flow based on the numerical data.
Masakiyo Kitazawa, Osaka University
[QCD Theory Seminar] Search for phase transitions in dense QCD in heavy-ion collisions
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QCD is believed to have various phase transitions at nonzero density and temperature. In this talk, I will discuss two topics related to their experimental searches in relativistic heavy-ion collisions. The first topic is concerned with a search for the QCD critical point using fluctuation observables. I will overview recent theoretical and experimental progress in this field especially focusing on the non-Gaussian fluctuations of conserved charges. I will then discuss a more ambitious subject to search for color superconductivity. Near the phase boundary of color superconducting phases, diquark fluctuations are enhanced as the soft mode of the phase transition. We show that these fluctuations cause an anomalous enhancement of the dilepton production rate at low invariant-mass region through the analysis of the photon self-energy including diquark fluctuations. We argue that this enhancement can be used for an experimental signal of the precursor of color superconductivity.
Hiromasa Watanabe, Tsukuba University
Confinement/deconfinement transition in the D0-brane matrix model -- A signature of M-theory?
Online (Zoom) https://kds.kek.jp/event/40652/
We study the confinement/deconfinement transition in the D0-brane matrix model (the BFSS matrix model) and its one-parameter deformation (the BMN matrix model) numerically by lattice Monte Carlo simulations. Our results confirm general expectations from the dual string/M-theory picture for strong coupling. In particular, we observe the confined phase in the BFSS matrix model, which seems a nontrivial consequence of the M-theory picture. We suggest that these models provide us with an ideal framework to study the Schwarzschild black hole, M-theory, and furthermore, the parameter region of the phase transition between type IIA superstring theory and M-theory. This talk is based on the paper arXiv:2110.01312. In addition, the connection between string theory and M-theory in the context of the BFSS matrix model will be overviewed.
Kiyoharu Kawana, Seoul National University
Multi-critical point principle and its Phenomenology
Online (Zoom) https://kds.kek.jp/event/40651/
Multi-critical point principle (MPP) is an interesting theoretical possibility, which claims that coupling constants of low energy effective theory are tuned to the point where the vacuum structure or history of the Universe changes drastically. In this talk, I will try to explain the basic concepts and ideas of the MPP without going into the details of underlying physics. Then, I will present a few phenomenological applications of this principle, including our recent works (arXiv:2107.10720 and paper in preparation).
Yuuki Hayashi, Tohoku University
Renormalon subtraction using Fourier transform - towards precise QCD calculation
Online (Zoom)
