Goro Ishiki, University of Tsukuba
Diffeomorphisms and Berezin-Toeplitz quantization for fuzzy spaces
Seminar room, Kenkyu honkan 3F
In the matrix model formulations of string/M- theories, geometry of strings/branes is expressed in terms of configurations of matrices. We discuss how the diffeomorphism, which is one of the most important symmetry in the world volume theory of strings and branes, is realized in the configuration space of matrices. We show that the diffeomorphism for matrices can be defined by using the so-called Berezin-Toeplitz quantization. As an example, we consider the fuzzy S^2 and explicitly construct the matrix version of the holomorphic diffeomorphisms on the fuzzy S^2.
Yoshifumi Hyakutake, Ibaraki University
Inflationary Cosmology via Quantum Corrections in M-theory
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
Inflation is a promising scenario to resolve problems of big bang cosmology, such as horizon problem. Although there are a lot of models which realize the inflation, it is natural to explain it in the framework of quantum gravity. In this talk, we consider 11 dimensional M-theory, which consists of the 11 dimensional supergravity and quartic terms of the Weyl tensor, as the theory of quantum gravity, and investigate inflationary cosmology by analyzing the effective action of the M-theory. We will show that the classical solution of the 11 dimensional supergravity does not represent the inflationary expansion, but if we include the quantum corrections, the behavior of the solution around the very early time is modified and the inflationary scenario is realized.
Alexander Kusenko, UCLA and Kavli IPMU
Primordial black holes as dark matter
Meeting room 3, Kenkyu honkan 1F
I will discuss new and rather generic scenarios for production of black holes in the early universe. In some mass range, such black holes can account for all dark matter. Primordial black holes can also contribute to synthesis of heavy elements by disrupting neutron stars.
Takeru Yokota, Department of Physics, Kyoto University
Functional renormalization group-aided density-functional theory - application to one-dimensional nuclear matter and two-dimensional electron gas -
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
The functional renormalization group-aided density-functional analysis (FRG-DFT) starts to be applied to realistic models of quantum many-body systems. Recently we have developed a new FRG-DFT formalism, which is suitable for analyzing systems with an infinite number of particles with fixed densities. In this talk, I will present our formalism and our two applications: The first one is the calculation of the equation of state (EOS) and the density-density spectral function of an infinite nuclear matter (NM) in (1+1) dimensions composed of spinless nucleons. The resultant EOS of the NM coincides with that obtained by the Monte-Carlo method within a few percents for the available range of density. We also reproduce a notable feature of the density spectral function of the non-linear Tomonaga-Luttinger liquid: The spectral function has singularities at the edge of its support at the lower-energy side. Subsequently, I will show our FRG-DFT analysis of the two-dimensional homogeneous electron gas, which is the first application of FRG-DFT to two-dimensional systems. We find that the result of FRG-DFT reproduces the exact correlation energy at the high-density limit and is consistent with the Monte-Carlo results for the high- and mid-density cases. Our study demonstrates that the FRG-DFT can be a promising method to analyze quantum many-body systems.
Yu-tin Huang, Department of Physics, National Taiwan University
Build the wall and drain the swamp: positive constraints on EFT from the UV
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
In this talk I will introduce new constraints on couplings of operators in effective field theory derived from Unitarity and Lorentz invariance in the UV. These constraints come in the form of positive geometries in the space of couplings. The origin of this positivity originates from the remarkable positive properties of Gegenbauer polynomials, which are the basis polynomials dictated by Lorentz invariance. Unitarity then dictates that the discontinuity of the S-matrix has a positive expansion on these polynomials. This double positivity give rises to the mathematical object that we named the “EFThedron”, for which all consistent QFT must reside in. Adding that the underlying theory has a worldsheet description, allows us to begin to carve out the string landscape in an on-shell fashion.
Yasunori Lee, Kavli IPMU
A study of time-reversal symmetry of Abelian anyons
Meeting room 3, Kenkyu honkan 1F, slides (kek.jp only)
(2+1)d TQFTs have been studied from various points of view. Recently, the actions of discrete symmetries on them are attracting attention in the context of topological phases of matter. In this talk, I will first review the basic concepts and formalism, and then present the analysis of time-reversal symmetries on Abelian anyon systems mainly focusing on their anomaly.
Takeshi Morita, Shizuoka University
Quantum quench of one-dimensional Fermi gas and thermalization to generalized Gibbs ensembles
Seminar room, Kenkyu honkan 3F, slides (kek.jp only)
Understanding thermalization and entropy production is one of the outstanding problem in theoretical physics. However, in integrable systems, we can explicitly solve the time evolution and observe thermalization to so called generalized Gibbs ensembles. In this talk, we demonstrate it in one-dimensional free Fermi gas, which are trapped in external potentials or a circle, through quantum quenches. We analytically compute local observables such as particle density and show that they always exhibit power law relaxation at late times. We find a simple rule which determines the power law exponent. Our findings are, in principle, observable in experiments in an one dimensional free Fermi gas or Tonk’s gas (Bose gas with infinite repulsion).
Keiichi Maeda, Kyoto University
Constraining progenitors and explosion mechanisms of supernovae through their nucleosynthesis characteristics
Meeting room 3, Kenkyu honkan 1F, slides (kek.jp only)
Supernovae (SNe) are the explosive death of stars, either triggered by gravitational collapse of massive stars (CCSNe; core-collapse SNe) or thermonuclear runway of a white dwarf (SNe Ia). Identifying the natures of their progenitors and explosion mechanisms is one of the central issues in stellar astrophysics and observational transient science. In this talk, I will first introduce basic concepts of the SN explosion nucleosynthesis. Then, a review is given on how different progenitors and explosion mechanisms would manifest themselves in observational properties of SNe. Finally, I will quickly go through some examples of recent progresses in individual topics, where the observational data are used to constraint the natures of the progenitors and explosions through the nucleosynthesis arguments; (1) the white dwarf masses and modes of thermonuclear runaway in SNe Ia, (2) the masses of progenitor stars for different classes of CCSNe, and (3) the standard neutrino-driven explosion models and beyond as confronted by the observations of CCSNe and peculiar outliers (such as those associated with Gamma-Ray Bursts).
Tim Maudlin, New York University
What is Wavefunction Realism?
Seminar room, Kenkyu honkan 3F
In the foundations of physics literature, the question is sometimes raised about whether one should—or even can—be a realist about the wavefunction. This query offers two targets for analysis and explication: “realist” and “wavefunction”. The first term is used in many different ways, as is the second, and to get down to a non-trivial and sensible question one has to specify exactly what one has in mind. I will argue that given the only sensible and non-trivial way to make a clear question here, the indeed one ought to be a “realist” about the “wavefunction”. There never should have been much controversy here, and the recent theorem by Pusey, Barrett and Rudolph settles the issue.
Anupam Mazumdar, University of Groningen
Scale free theory of infinite derivative gravity in the ultraviolet
Seminar room, Kenkyu honkan 3F
