Soeren Schlichting, Bielefeld University
[QCD theory Seminar] Dynamic critical behavior in the Z_2 Ising and O(4) universality classes
In this talk I will discuss the dynamic critical behavior of relativistic scalar field theories, with dissipative (Model A), diffusive (Model B) and conservative (Model C/D) dynamics. Based on first principle simulations, I will discuss the manifestations of the critical behavior in real-time correlation functions and extract universal scaling functions that describe the spectral functions of the order parameter in the vicinity of the critical point. If time remains I will also present preliminary results for the evolution of cumulants of the order parameter in non-equilibrium phase transitions, where a system dynamically transits the critical point in the phase diagram.
Neill Warrington, University of Washington
Contour Deformations for Lattice Field Theory
Highly oscillatory path integrals are common in lattice field theory.
They crop up as sign problems and as signal to noise problems and prevent Monte Carlo calculations of both lattice QCD at finite chemical potential and real-time dynamics. A general method for treating highly oscillatory path integrals has emerged in which the domain of integration of the path integral is deformed into a complexified field space. In this talk I will review this method, and I will discuss recent progress in machine learning manifolds for lattice QCD.
Masaru Hongo Affiliation, University of Illinois Chicago
[QCD theory Seminar] Relativistic spin hydrodynamics with torsion and linear response theory for spin relaxation
Recent experimental observation of spin polarization of hadrons in relativistic heavy-ion collisions [1] motivates the development of the theory describing spin transport in relativistic plasma. In this talk, I will introduce our recent work on a theoretical formulation of relativistic spin hydrodynamics based on the second law of local thermodynamics and linear response theory [2]. We work in a regime where spin density, which is assumed to relax much slower than other non-hydrodynamic modes, is treated as an independent degree of freedom in an extended hydrodynamic description. Spin hydrodynamics in our approach contains only three non-hydrodynamic modes corresponding to a spin vector, whose relaxation time is controlled by a new transport coefficient, the rotational viscosity. Using the derived constitutive relation, I will explain our main results; an interesting mode mixing phenomenon between the transverse shear and the spin density modes, and several field-theoretical ways to compute the rotational viscosity via the Green-Kubo formula based on retarded correlation functions.
References:
[1] STAR Collaboration, L. Adamczyk et al., Nature 548 (2017) 62?65, arXiv:1701.06657 [nucl-ex]
[2] M. Hongo, X-G. Huang, M. Kaminski, M. Stephanov, H-U Yee, arXiv:2107.14231 [hep-th]
[1] STAR Collaboration, L. Adamczyk et al., Nature 548 (2017) 62?65, arXiv:1701.06657 [nucl-ex]
[2] M. Hongo, X-G. Huang, M. Kaminski, M. Stephanov, H-U Yee, arXiv:2107.14231 [hep-th]
Boram Yoon, LANL
Machine Learning Prediction and Compression of Lattice QCD Observables
In lattice QCD simulations, a large number of observables are measured on each Monte Carlo sample of the QCD universe, called gauge configuration. Since the measured observables share the same background gauge configuration, their statistical fluctuations are correlated with each other, and analyzing such correlation is a well-suited problem for machine learning (ML) algorithms. In this talk, I will present two ML applications to lattice QCD problems: (1) prediction of unmeasured-but-computationally-expensive observables from the cheap observables on each gauge configuration, and (2) compression of lattice QCD data using D-Wave quantum annealer as an efficient binary optimization algorithm. For both applications, a bias correction algorithm is applied to estimate and correct the systematic error due to inexact ML predictions and reconstruction.
Robert Brandenberger, McGill University
Superstring Theory and Cosmology of the Very Early Universe
At the present time, cosmology is presenting us with a wealth of data which can only be explained by invoking new physics operating in the very early universe. I will introduce three paradigms for the evolution of the early universe: inflation, a cosmological bounce, and an emergent scenario. I will argue that in light of arguments from quantum gravity and string theory the inflationary paradigm is severely constrained.
I will then discuss attempts to obtain an emergent cosmology making use of fundamental principles of superstring theory, in particular matrix theory.
Sotaro Sugishita, Nagoya University
Target space entanglement in quantum mechanics of fermions and matrices
I will introduce the notion of target space entanglement. Quantum entanglement is closely related to the structure of spacetime in quantum gravity. For quantum field theories or statistical models, we usually consider the base space entanglement. However, target space instead of base space sometimes directly connects to our spacetime, for example, perturbative string theories. We thus need target space entanglement. To define the target space entanglement, we have to generalize the definition of the conventional entanglement entropy. I will explain this generalization and apply it to the first quantized particles, in particular, fermions.
Yuki Fujimoto, University of Tokyo
[QCD Theory Seminar] Non-Abelian Alice strings in two-flavor dense QCD
Recently, the new phase of the two-flavor color superconductor was proposed in connection with the recent discussion on the equation of state of neutron stars [1]. In this talk, I will show the classification of the topological vortices in this phase. We found that the most stable vortices are what we call the “non-Abelian Alice strings” [2]. They are superfluid vortices carrying 1/3 quantized circulation and color magnetic fluxes. I will discuss in some details about their properties in comparison to the well-established CFL vortices in three-flavor symmetric setup, by putting some emphasis on their peculiarity: the non-Abelian generalization of the Alice property. I will also discuss the confinement of the vortices as well as how the vortices in the quark phase are connected to those in the hadronic phase [3].
References:
[1] Y. Fujimoto, K. Fukushima, W. Weise, Phys. Rev. D 101, 094009 (2020), arXiv:1908.09360 [hep-ph].
[2] Y. Fujimoto, M. Nitta, Phys. Rev. D 103, 054002 (2021), arXiv:2011.09947 [hep-ph]; JHEP 09 (2021) 192, arXiv:2103.15185 [hep-ph].
[3] Y. Fujimoto, M. Nitta, Phys. Rev. D 103, 114003 (2021), arXiv:2102.12928 [hep-ph].
[1] Y. Fujimoto, K. Fukushima, W. Weise, Phys. Rev. D 101, 094009 (2020), arXiv:1908.09360 [hep-ph].
[2] Y. Fujimoto, M. Nitta, Phys. Rev. D 103, 054002 (2021), arXiv:2011.09947 [hep-ph]; JHEP 09 (2021) 192, arXiv:2103.15185 [hep-ph].
[3] Y. Fujimoto, M. Nitta, Phys. Rev. D 103, 114003 (2021), arXiv:2102.12928 [hep-ph].
Andrey Shkerin, University of Minnesota
Black hole induced false vacuum decay from first principles
We will discuss a method to calculate the rate of false vacuum decay induced by a black hole. The method uses complex tunnelling solutions and consistently takes into account the structure of quantum vacuum associated to the black hole. We will illustrate the technique on a two- dimensional toy model of a scalar field with inverted Liouville potential in an external background of a dilaton black hole. Using this model, we will compute the exponential suppression of tunnelling from the Boulware, Hartle-Hawking and Unruh vacuum states and show that they are parametrically different. Finally, we will discuss how our results are generalised to the realistic case of black holes in four dimensions.
Benjamin Grinstein, University of California San Diego
[EX] The Neutron Decay Anomaly: a window to new Physics, perhaps.
In this talk I will first review a long-standing discrepancy between the neutron lifetime as measured in beam and in bottle experiments. If this discrepancy is not due to a systematic error, it may be due to novel mechanisms for neutron transmutation into new, as yet unknown elementary particles. These particles would be electrically neutral, or so-called “dark”. We will explain several scenarios for the possibility of neutron transmutation into dark particles. For example, in one interesting scenario the products of the neutron transmutation include a monochromatic photon with energy in the range 0.782 MeV?1.664 MeV and this is predicted to occur in 1% of all neutron decays. We will describe recent theoretical developments as well as ongoing and planned experiments looking directly to establish or rule out the “dark decay” hypothesis.
松本 伸之, 学習院大学
[KEK連携コロキウム] 量子振り子の開発と応用