Takahiko Terada, Nagoya U
Dissipative Genesis of the Inflationary Universe
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
We study an inflation model with a flat scalar potential supported by observations and find that slow-roll inflation can emerge after a quasi-cyclic phase of the Universe, where it undergoes repeated expansions and contractions for a finite time period. The initial conditions and the positive spatial curvature required for such nontrivial dynamics align with the quantum creation of the Universe. The key ingredients that trigger inflation are dissipative interactions of the inflaton, which are necessary to reheat the Universe after inflation and thus give us an observational handle on pre-inflationary physics. Our discovery implies that inflation occurs more robustly after the creation.
Yuta Michimura, RESCEU
Laser interferometric searches for ultralight dark matter
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
Despite overwhelming observational evidence for the existence of dark matter, its identity and properties remain a mystery. Bosonic ultralight fields with masses below 1 eV are gaining a lot of attention, as they are well motivated by cosmology. Laser interferometers are sensitive to oscillations from such fields that change the interference fringe. Recently, we have proposed to search for axion dark matter by measuring the birefringence effect using a bow-tie optical ring cavity [PRL 121, 161301 (2018)] and gravitational wave detectors [PRL 123, 111301 (2019)]. We have also proposed to search for vector dark matter by searching for non-standard force acting on mirrors [PRD 102, 102001 (2020)]. In this talk, I will present some of the first results from a table-top experiment, Dark matter Axion search with riNg Cavity Experiment (DANCE) [PRD 108, 072005 (2023)], and the status of axion and vector dark matter searches using gravitational wave detectors.
Toshifumi Futamase, Tohoku University
An interpretation of Hubble tension and S8 tension by the observed Inhomogeneous matter density
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
Hubble parameter describes the expansion rate of the universe and is one of the most important parameter to characterize our universe. Thus, the measurement has been a major topic in the observational cosmology. Recently there has been a significant discrepancy in the measured value depending on the method of the observation. This is called as the Hubble tension. If the discrepancy is real, it will cause a revolutionary change in the standard cosmology. Not only Hubble parameter but also recent galaxy survey reported a similar discrepancy in the structure formation parameter S8 from CMB measurement. On the other hand, there is observational evidence by the observation of K-band luminosity density that our galaxy is in a low-density region of the order of three hundred Mega parsec. We consider the effects of this inhomogeneous matter distribution on the Hubble parameter and S8 parameter. For this purpose, Einstein equation is averaged over an arbitrary finite region to construct local Friedman universe which is characterized by local cosmological parameters, and thus we can derive the relation between local and horizon scale cosmological parameters. According to this relation we can explain the observed discrepancies of Hubble parameter and S8 without introducing any new physics.
Ryan Hill, The university of Edinburgh
Variance-Reduction Techniques for Disconnected Isospin-Breaking QED Corrections
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
Sub-percent calculations of an increasing number of physical observables are within the reach of modern Lattice QCD. In order to achieve such precision, we must include the (typically) O(1%) corrections from isospin-breaking contributions in our calculations. These corrections include disconnected diagrams, which can be prohibitively expensive to resolve using standard techniques. In this talk, I will discuss ongoing efforts to calculate several disconnected topologies relevant at O(alpha) to e.g. Kl2 decays, on RBC-UKQCD physical-point domain-wall ensembles, following on from exploratory calculations [1]. We make use of the ‘split-even’ estimator [1, 2], which can improve statistical errors by an order of magnitude or more, and explore the use of a distance-splitting technique [1] to take advantage of the dominant short-distance behaviour of some topologies. These techniques are applicable beyond disconnected diagrams, and might improve statistical errors in many contractions involving noisy loop estimators. I will explore the potential to make great improvements on the statistical error of our previous result for rare K+->Pi+l+l- decays [3] using these techniques.
[1] Harris, T., Gülpers, V., Portelli, A., Richings, J. Efficiently unquenching QCD+QED at O(alpha) PoS LATTICE2022 (2023). https://arxiv.org/abs/1903.10447
[2] Giusti, L., Harris, T., Nada, A. et al. Frequency-splitting estimators of single-propagator traces. Eur. Phys. J. C 79, 586 (2019). https://doi.org/10.1140/epjc/s10052-019-7049-0
[3] Boyle, P. A., Erben, F., Flynn, J. M., Gülpers, V., Hill, R. C., Hodgson, R., Jüttner, A., Ó hÓgáin, F., Portelli, A., Sachrajda, C. T. Simulating rare kaon decays K+->Pi+l+l- using domain wall lattice QCD with physical light quark masses. Phys. Rev. D 107 (2023) L011503. https://link.aps.org/doi/10.1103/PhysRevD.107.L011503
Rahool Kumar, IPMU
Machine learning the Higgs-top CP measurement at the LHC
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
The conventional approach to LHC analysis involves comparing the measured data to Monte Carlo simulations. These simulations start at the hard-scattering level, where the potential for new physics is maximal, and proceed through various stages, including showering, hadronization, and detector response. Unfortunately, each stage introduces complexities, resulting in a convoluted representation of the true underlying physics at the simulated detector level. Events measured at the LHC detector are also somewhat convoluted versions of the true underlying physics due to various latent effects. Eliminating these convolutions is essential for a direct comparison between theoretical predictions and measured data, which can be achieved through the process of ‘Unfolding’, where measured events are directly mapped to the hard-scattering level.
Yuri Michinobu, YITP
Species bound and its moduli dependence
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom The species bound, a swampland conjecture, suggests that the cutoff of quantum gravity in an effective field theory coupled to a number of light fields is significantly lower than the Planck scale. Notably, the species bound offers insights into the interior of the moduli space. In this talk, I will review recent progress in this direction (2303.13580,2212.10286). I will begin by introducing the notion of the species bound and then discuss constraints on its dependence on moduli. Additionally, I will explain the connection to black hole entropy, which serves as a
The species bound, a swampland conjecture, suggests that the cutoff of quantum gravity in an effective field theory coupled to a number of light fields is significantly lower than the Planck scale. Notably, the species bound offers insights into the interior of the moduli space. In this talk, I will review recent progress in this direction (2303.13580,2212.10286). I will begin by introducing the notion of the species bound and then discuss constraints on its dependence on moduli. Additionally, I will explain the connection to black hole entropy, which serves as a
non-trivial check of the constraint.
Adil Jueid, Institute for Basic Science
[cancelled] Dark matter triggering flavor changing neutral current decays of the top quark
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
In this talk, I will discuss a possible connection between dark matter (DM) and one-loop induced top quark FCNC decays. In a simplified t-channel DM model that extends the SM with one colored scalar mediator and one right-handed fermion both odd under an ad-hoc Z_2 symmetry, I will show that that moderate to large rates of the top quark FCNC decays are possible while respecting the existing constraints. Then I will discuss the phenomenological implications at hadron colliders (HL-LHC and FCC-hh) of four phenomenologically viable scenarios.
Tokiro Numasawa, ISSP
Gauging Spacetime Inversions
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom Spacetime inversion symmetries such as parity and time reversal play a central role in physics, but they are usually treated as global symmetries.
Spacetime inversion symmetries such as parity and time reversal play a central role in physics, but they are usually treated as global symmetries.
In quantum gravity there are no global symmetries, so any spacetime inversion symmetries must be gauge symmetries.
In particular this includes CRT symmetry (in even dimensions usually combined with a rotation to become CPT), which in quantum field theory is always a symmetry and seems likely to be a symmetry of quantum gravity as well.
In this talk, we will discuss what it means to gauge a spacetime inversion symmetry and explain some of the more unusual consequences of doing this.
In particular, I will argue that the gauging of CRT is automatically implemented by the sum over topologies in the Euclidean gravity path integral, that in a closed universe the Hilbert space of quantum gravity must be a real vector space, and that in Lorentzian signature manifolds which are not time-orientable must be included as valid configurations of the theory.
Tetsuo Hyodo, Tokyo Metropolitan University
[KEK-JAEA Joint Seminar] Femtoscopy for Exotic Hadrons and Nuclei
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom In high-energy collision experiments, the momentum distribution of hadron pairs reveals correlations arising from hadron interactions and quantum statistics. Traditionally, femtoscopy has been used to derive emission source information from these correlations. Recently, these techniques have also facilitated new methods to assess hadron
In high-energy collision experiments, the momentum distribution of hadron pairs reveals correlations arising from hadron interactions and quantum statistics. Traditionally, femtoscopy has been used to derive emission source information from these correlations. Recently, these techniques have also facilitated new methods to assess hadron
interactions, as exemplified by the ALICE collaboration’s significant advancements at the LHC. This talk will cover the fundamental theoretical methods for calculating momentum correlation functions and discuss recent applications to antikaon-nucleon systems and hypernuclei, with a look toward future research at J-PARC.
References:
[1] S. Cho et al., ExHIC collaboration, Prog. Part. Nucl. Phys. 95, 279 (2017).
[2] Y. Kamiya, T. Hyodo, K. Morita, A. Ohnishi, W. Weise, Phys. Rev. Lett. 124, 132501 (2020).
[3] A. Jinno, Y. Kamiya, T. Hyodo, A. Ohnishi, arXiv:2403.09126 [nucl-th]
Kiyoharu Kawana, KIAS
Fine-Tuning as Quantum Phase Transition Point
Online (Zoom) We discuss analogy between statistical mechanics and quantum field theory from the point of view of fine-tuning problem. In the former, (first-order) phase transition (PT) point spans a finite parameter space in micro-canonical ensemble, while it is literally a point and looks like a fine-tuning of parameters in canonical ensemble.
