2021/12/13 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: A brief introduction to the model of solid inflation

Speaker: Koki Tokeshi

Abstract: Many inflationary models can be treated in the framework of the conventional effective field theory approach, in which the time translation symmetry slightly breaks to realize quasi de Sitter Universe [2]. The model of solid inflation, proposed and systematically analyzed in [1], gives an exception: the spatial translation symmetries are broken in the model. In this talk, I will review the model and introduce many unusual features stemmed from the drastically different symmetry breaking pattern. Since the scalar amplitude could be enhanced compared to the conventional prediction, I will also discuss possibility of black hole formation in the model [3].
References:
[1] S. Endlich, A. Nicolis, and J. Wang, ‘Solid inflation,’ JCAP 10 (2013) 011.
[2] C. Cheung, L. Fitzpatrick, J. Kaplan, and L. Senatore, ‘The effective field theory of inflation,’ JHEP 03 (2008) 014.
[3] G. Ballesteros, J. Jimenez, M. Pieroni, ‘Black hole formation from a general quadratic action for inflationary primordial fluctuations,’ JCAP 06 (2019) 016.

2021/11/29 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: Introduction to generalized global symmetries and their application

Speaker: Yoshimasa Hidaka

Ordinary symmetries are symmetries acting on point particles. The concept can be generalized to symmetries acting on extended objects, such as vortices and domain walls. Such symmetres are called higher form symmetries. In this talk, I review the concept of higher form symmetries. As an example of the application, I discuss spontaneous breaking of higher form symmetries in a nonrelativistic system and show the counting rule of the Nambu-Goldstone modes.

2021/11/22 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Dear all,

Next RESCEU Monday seminar is on Nov. 22, 15:30-16:30.
The seminar is the continuation of the last seminar, and the information is as follows.

=======================================================================

Title:Two-group symmetry in QED

Speaker:Fumio Uchida

Abstract:
Symmetry is one of the most fundamental concepts in physics. However, well-known symmetries as of the Standard Model belong to just the simplest class of its generalizations [1-3]. In the talk, we will see two-group symmetry in massless and multi-flavor QED, as an explicit example of the wider symmetry class. I hope the talk will be complementary to the forthcoming lecture [4].

Refs:
[1] D. Gaiotto, et al. “Generalized global symmetries,” JHEP 02, 172 (2015), arXiv:1412.5148 [hep-th].
[2] E. Sharpe, “Notes on generalized global symmetries in QFT,” Fortsch. Phys. 63, 659 (2015), arXiv:1508.04770 [hep-th].
[3] C. Cordova, et al. “Exploring 2-Group Global Symmetries,” JHEP 02, 184 (2019), arXiv:1802.04790 [hep-th].
[4] Prof. Hidaka’s lecture, assigned to the next slot of our seminar series, about generalized symmetry.

2021/11/15 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: Hawking radiation as quantum tunneling

Speaker: Takumi Hayashi

Abstract: Hawking radiation is a thermal radiation induced by a black hole, which is predicted by quantum field theory in curved spacetime. There are several attempts to formulate Hawking radiation as quantum tunneling of an emitted particle, which succeed in capturing the feature of it. Since the tunneling method is simpler than the original field theory, there exist important applications to the dynamical black hole providing an insight into information loss paradox.
In this talk, I will review the tunneling method of Hawking radiation and generalization to the case with back reaction to black hole. I will also briefly introduce the recent works which discuss the information loss on the basis of the method.

[1] K. Srinivasan and T. Padmanabhan, Phys. Rev. D 60 (1999), 024007
[2] M. K. Parikh and F. Wilczek, Phys. Rev. Lett. 85 (2000), 5042-5045
[3] B. Zhang, Q. y. Cai, L. You and M. s. Zhan, Phys. Lett. B 675 (2009), 98-101
[4]P. Chen, M. Sasaki and D. H. Yeom, Eur. Phys. J. C 79 (2019) no.7, 627
[5]P. Chen, M. Sasaki and D. H. Yeom, arXiv:2111.01005

2021/11/8 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: Chirality generation via Schwinger Effect -real time description for CME-

Speaker: Jun'ya Kume

Abstract: The Chiral Magnetic Effect (CME) predicts electric current is induced by a magnetic field in the left-right asymmetric fermion background. Asymmetry of the background, or the transportation coefficient is conventionally expressed by the so-called chiral chemical potential. Due to such a proportionality, CME current is sometimes misunderstood as an equilibrium response, but it is not the case. In this talk, I will give a review on the Schwinger pair production with parallel E and B. Such a field configuration generates chiral asymmetry and chiral chemical potential does not enter in the production rate. In order to clarify the real-time nature of the CME, in-in evaluation of the chiral charge and the electric current is performed in such a system.

References:
[1]P. Copinger, K. Fukushima and Shi Pu, Phys.Rev.Lett. 121 (2018) 26, 261602
[2]P. Copinger and Shi Pu, Int.J.Mod.Phys.A 35 (2020) 28, 2030015
[3]G. V. Dunne, hep-th/0406216[hep-th]

2021/11/1 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: Universality class and the chiral phase transition in QCD

Speaker: Kohei Fujikura

Landau-Ginzburg-Wilson (LGW) theory, based on the argument of universality, is a powerful effective theory that describes the dynamics of various phase transitions [1,2]. Pisarski and Wilczek constructed the LGW Hamiltonian of the QCD chiral phase transition and analyze the dynamics of the phase transition at one-loop order. They concluded that the phase transition is of (fluctuation-induced) first order for two or more massless quarks when U(1)_A is fully recovered during the phase transition [3]. In this talk, I will review the argument of universality and its application to QCD (chiral) phase transition.

References:
[1] K.G.Wilson and M. E. Fisher Critical Exponents in 3.99 Dimensions, Phys. Rev. Lett. 28, 240
[2] M. E. Fisher, The renormalization group in the theory of critical behavior, Rev. Mod. Phys. 47, 543 (1975).
[3] R. D. Pisarski and F. Wilczek, “Remarks on the chiral phase transition in chromodynamics,”

2021/10/4 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Singularities of Cosmological Correlators

Jason Kristiano

Abstract: The structures of the cosmological correlators are controlled by their singularities [1,2], which are fixed in terms of the flat-space scattering amplitude [3]. By knowing their singularities, residues, and unitarity conditions, it is possible to determine the full structure of the correlators. This method was proposed by Baumann et. al. in their latest paper [1] within the spirit of the bootstrap method, much influenced by [2] and [3] paper. This will be a series of lectures, with tentative contents:

(1) Oct 4: Singularities of flat-space correlators and de-Sitter space correlators.
(2) TBD: Cutting correlators and gluing correlators rules.
(3) TBD: Lifting correlators rules, from flat-space to de-Sitter space.

References:

[1] D. Baumann, et. al., Linking the Singularities of Cosmological Correlators, arXiv:2106.05294
[2] S. Jazayeri, et. al., From locality and unitarity to cosmological correlators, arXiv:2103.08649
[3] N. Arkani-Hamed, et. al., Cosmological Polytopes and the Wavefunction of the Universe, arXiv:1709.02813

2021/9/27 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Gravitational Wave Probes of Dark Matter and the Baryon Asymmetry from Axion Rotations

Raymond Co

Abstract:
We establish a paradigm where the (QCD) axion’s novel cosmological evolution, a rotation in the field space, gives rise to dark matter and the baryon asymmetry. The axion rotations also provide a natural origin for a kination era, where the total energy density is dominated by the kinetic term of the axion field, preceded by an early era of matter domination. We investigate the effects of this cosmological scenario on the spectrum of possible primordial gravitational waves from inflation or cosmic strings and find that the spectrum features a triangular peak. As a result, future gravitational wave observations can probe the viable parameter space of kination, including regions that produce axion dark matter by the kinetic misalignment mechanism or the baryon asymmetry by axiogenesis.

References:
[1] https://arxiv.org/abs/2108.09299
[2] https://arxiv.org/abs/1910.02080
[3] https://arxiv.org/abs/1910.14152

2021/7/26 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: On the excitation of black hole overtones

Speaker: Naritaka Oshita

Abstract: Understanding the nature of quasinormal ringing of black holes is important in the context of
gravitational wave (GW) astronomy, gauge/gravity correspondence, and even quantum gravity.
In this motivation, I will briefly review the essence of excitation factors of a ringing black hole.
The excitation factor quantifies the “ease-of-excitation” of the quasinormal modes of the black hole,
which may be an important ingredient to predict when the ringdown phase starts in GW signal
emitted by a binary black hole merger. I will also explain the recent progress, including my
preliminary result about the excitation factor of black hole overtones.

2021/7/19 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: SU(N) gauge natural inflation

Speaker: Tomohiro Fujita

Abstract: I'll discuss general attractor solutions for SU(N) gauge fields coupled to a rolling axion via the Chern-Simons interaction during inflation. It has been known that the SU(2) gauge field has an isotropic and homogeneous attractor solution, which leads to rich phenomenology including the amplification of primordial gravitational waves. We find a generic way to construct similar background solutions for SU(N), and enumerate all the isotropic stationary solutions for SU(3) and SU(4). We also confirm that numerical solutions with random initial conditions converge into these attractors. Interestingly, the gauge field amplitudes (i.e. VEVs) tend to increase as N of SU(N) grows, which may provide interesting observational signatures.

2021/7/12 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: Black hole information paradox and fine grained entropy in gravitational system

Speaker: Yusuke Yamada

Black hole information paradox has been one of the unsolved problems in quantum gravity. One can quantify the problem by looking at the behavior of the von Neumann entropy, which is also known as fine-grained entropy. Recently, the solution to the information paradox was proposed, which is the new rule to obtain improved fine-grained entropy formula in gravitational system. The improved formula gives the fine-grained entropy consistent with the unitarity.
Interestingly, it can be derived by the semiclassical method, which is unexpectedly simple.
In this talk, I will briefly review the information paradox and review the derivation of the fine-grained entropy formula in gravitational system, which is crucial to understand the recent proposals. If I have time, I will also explain how the expected behavior of the entropy, known as Page curve, is realized. (It is quite unlikely to have enough time, though.)

Refs:
A. Almheiri, T. Hartman, J. Maldacena, E.Shaghoulian, A. Tajdini, “The entropy of Hawking radiation” [2006.06872]
A. Lewkowycz, J. Maldacena, “generalized gravitational entropy” [1304.4926]
T. Faulkner, A. Lewkowycz, J. Maldacena, “Quantum corrections to holographic entanglement entropy” [1307.2892]
X. Dong, A. Lewkowycz, “Entropy, extremality, euclidean variations, and the equations of motion” [1705.08453]
A. Almheiri, T. Hartman, J. Maldacena, E.Shaghoulian, A. Tajdini, “Replica Wormholes and the Entropy of Hawking Radiation” [1911.12333]
G. Penington, S. Shenker, D. Stanford, Z. Yang, “Replica wormholes and the black hole interior” [1911.11977]

2021/7/5 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: Ceterum autem censeo, Gravitas esse quantizo

Speaker: Kohei Kamada

Niels Bohr has once argued in his private communications
that the consistency of the double-slit experiment of charged particle
with the detectors that can measure the Coulomb force
requires the quantization of the electromagnetic fields.
Motivated by the idea, recently people have studied the necessity
for the quantization of gravitons.
In this talk, I will introduce two studies on that,
where the later one concluded that graviton must be quantized.

Refs.
[1] Baym & Ozawa, PNAS 106, 3035, 2009, arXiv: 0902.2615 [quant-ph]
[2] Belenchia et al., PRD 98, 126009, 2018, arXiv:1807.07015 [quant-ph]

2021/6/28 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: Environmental noise estimation and detector characterization of gravitational wave detectors

Speaker: Jun’ichi Yokoyama

In the first part, I will introduce our recent paper
on environmental noise estimation via injection
test toward removing them to improve sensitivity.
Then I will introduce works on detector characterization
which remove transient noises using auxiliary channels
to obtain cleaner data of strain channel.

References:
T. Washimi, T. Yokozawa, T. Tanaka, Y. Itoh, J. Kume, and J. Yokoyama Class. Quantum Grav 38(2021)125005 [arXiv:2012.09294 [gr-qc]]

2021/6/21 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

An Introduction to skyrmions

Fumio Uchida

Abstract:
In the last decade there seems to be a trend of studying skyrmions [1], mostly in the field of condensed matter physics. Although we are in the field of not condensed matter physics but cosmology, it could be worth understanding the concept of it, since it is a family of the important concepts in cosmology, e.g., monopoles, cosmic strings, and domain walls, in that they all are topological solitons. In the talk, I will introduce magnetic skyrmions [2], which are the very concept attracting much attention from condensed matter physicists, and also talk about skyrmion dark matter [3], in the context of cosmology.

References:
[1] T. H. R. Skyrme, “A Nonlinear field theory,” Proc. Roy. Soc. Lond. 260 (1961) 127,
[2] A. N. Bogdanov and D. A. Yablonskii, “Thermodynamically stable ‘vortices’ in magnetically ordered crystals. The mixed state of magnets,” Zh. Eksp. Teor. Fiz 95 (1989) 178,
[3] H. Murayama and J. Shu, “Topological Dark Matter,” Phys. Lett. B 686 (2010) 162. [arXiv:0905.1720 [hep-ph]]

2021/6/7 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: Quantum Simulation (for cosmology?)

Speaker: Soichiro Hashiba

Abstract:
Quantum computing is one of the most rapidly progressing fields in science. Nowadays, quite a few people try to use quantum computers in cosmology. The most straightforward use of quantum computer is the quantum simulation by which we can simulate (in other words, make analogy experiments of) quantum phenomena in the early Universe. In this talk, I will explain the concept of quantum simulation [1] and show some primitive examples [2,3]. Current quantum computers, however, are too noisy for practical simulations. Therefore, I will also give a brief explanation of a quantum-classical hybrid method called the variational quantum eigensolver (VQE) [4] and recent examples of its application for cosmology [5,6].

References:
[1] M. Nielsen and I. Chuang, “Quantum Computation and Quantum Information”, Cambridge University Press (2000).
[2] C. Argüelles and B. Jones, Phys. Rev. Res. 1, 033176 (2019).
[3] B. Hall, A. Roggero, A. Baroni and J. Carlson, 2102.12556 [quant-ph].
[4] A. Peruzzo et al., Nat. Commun. 5, 4213 (2014).
[5] J. Stecenko, Y. Feng and M. McGuigan, 2105.02032 [quant-ph].
[6] A. Joseph et al., 2105.13849 [quant-ph].

2021/5/31 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Inflationary bispectrum from symmetry and locality.

Jason Kristiano

Abstract: Inflationary bispectrum was first derived by Maldacena in his famous paper [1]. Recently, inspired by the development of scattering amplitude in the particle physics community, some cosmologists are trying to derive inflationary bispectrum, or generally higher-point function, by only considering symmetries of cosmological perturbations. First, Nima Arkani-Hamed et. al. [2] successfully derived inflationary bispectrum by only using slightly broken de-Sitter space isometries. However, inflation generally breaks de-Sitter isometries, either small or large. For that motivation, Enrico Pajer et.al. [3-5] introduced a new bootstrap method without assuming de-Sitter isometries. In this seminar, I will review his method and compare the advantages and disadvantages to the previous one.

References:
[1] J. Maldacena, JHEP 05, 013 (2003).
[2] N. Arkani-Hamed, et. al., JHEP 04, 105 (2020).
[3] E. Pajer, JCAP 01, 023 (2021).
[4] S. Jazayeri, et.al., arXiv: 2103.08649.
[5] H. Goodhew et. al., JCAP 04, 021 (2021).

2021/5/24 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: Primordial black holes from fifth forces

Speaker: Koki Tokeshi

Primordial black holes could have formed in the early universe and various formation mechanisms have been proposed. Among them, I will review the relativly new one, first applied to PBHs in [1], in which the long range attractive forces between the light scalar and heavy fermion fields are exploited. I will also review the complementary paper [2], in which more general and quantitative analyses have been done, supporting the idea and estimations given in [1]. Related discussion about PBHs vs PMDHs in [3] and observational implications in [4] will also be reviewed.

References:
[1] Phys. Rev. D 97 (2018), 081302
[2] arXiv:2104.05271 (hep-th)
[3] Phys. Rev. D 100 (2019), 083518
[4] Phys. Rev. Lett. 126 (2021), 041101

2021/5/17 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: Entanglement harvesting from vacuum in cosmology

Speaker: Takumi Hayashi

Abstract:
Entanglement is a characteristic notion of quantum physics and important physical resources which can be used for quantum computation, quantum teleportation, and so on. Recently, the entanglement acquisition process in which an unentangled pair of cubits become entangled by the Unruh-Dewitt detector interaction with the vacuum of quantum field, called “entanglement harvesting”, has been well studied. In this talk, I review the entanglement harvesting process in various situations, including Minkowski spacetime and cosmological backgrounds. And I also introduce the case with cubits uniformly accelerated, which can induce the nontrivial resonant production of entanglement. I briefly mention recent works as well regarding this topic.

References:
[1] Martin-Martinez, Eduardo and Menicucci, Nicolas C., Class. Quantum Grav. 31, 214001 (2014),[arXiv:quant-ph/1408.3420], “Entanglement in curved spacetimes and cosmology”
[2] Reznik, B.; Retzker, A.; Silman, J., Phys. Rev. A 2005, 71, 042104, [arXiv:quant-ph/0310058], “Violating Bell’s inequalities in vacuum”.
[3] Steeg, G.V.; Menicucci, N.C., Phys. Rev. D 2009, 79, 044027, [arXiv:quant-ph0711.3066], “Entangling power of an expanding universe”.
[4] G. Salton, R. B. Mann, and N. C. Menicucci, New J. Phys. 17, 035001 (2015), [arxiv:quant-ph/1408.1395v2], “Acceleration-assisted entanglement harvesting and rangefinding”.

2021/5/10 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: Inflation from the point of view of quantum estimation theory

Speaker: Jun’ya Kume

Abstract: Recently, application of the quantum estimation theory to inflation has been discussed in several works by C. Gomez and R. Jimenez. Focusing on two of their papers, I introduce their perspectives that the properties of primordial curvature perturbation generated during inflation can be quantum mechanically explained by the quantum Fisher information with respect to the appropriate parameter. After I briefly give a review on the quantum Fisher information and Cramer-Rao bound, I present how the amplitude and the tilt of the curvature perturbation can be related to the Fisher information with respect to the time and the energy scale, respectively.

References:
[1]C. Gomez and R. Jimenez, Phys. Rev. D 102 (2020) no.6, 063511, [arXiv:2002.04294 [hep-th]].
[2]C. Gomez and R. Jimenez, arXiv:2012.04003 [hep-th].
[3]M. G. A. Paris, Int. J. Quantum. Inform. 07, 125 (2009).
[4]A. Albrecht, P. Ferreira, M. Joyce and T. Prokopec, “In-flation and squeezed quantum states,” Phys. Rev. D50,4807-4820 (1994) [arXiv:astro-ph/9303001 [astro-ph]]

2021/4/26 (月)

UTAPwiki/セミナー/初期宇宙・相対論速報

Title: Electroweak-like Baryogenesis with New Chiral Matter

Speaker: Kohei Fujikura

Abstract:
We propose a framework where a phase transition associated with a gauge symmetry breaking that occurs (not far) above the electroweak scale sets a stage for baryogenesis similar to the electroweak baryogenesis in the Standard Model. New chiral fermions charged under the extended gauge symmetry have nonzero lepton numbers, which makes the B-L symmetry anomalous. The new lepton sector contains a large flavor-dependent CP violation, similar to the Cabibbo-Kobayashi-Maskawa phase, without inducing sizable electric dipole moments of the Standard Model particles. A bubble wall dynamics associated with the first-order phase transition and sphaleron processes generate a lepton asymmetry, which is transferred into a baryon asymmetry via the ordinary electroweak sphaleron process. Unlike the Standard Model electroweak baryogenesis, the new phase transition can be of the strong first order and the new CP violation is not significantly suppressed by Yukawa couplings, so that the observed asymmetry can be produced. The model can be probed by collider searches for new particles and the observation of gravitational waves. This seminar is based on ref. [4].

References:
[1] G.R. Farrar and M.E. Shaposhnikov, “Baryon asymmetry of the universe in the minimal standard model" [hep-ph/9305275]
[2] M.B. Gavela, P.Hernandez, J. Orloff and O. Pene, “Standard Model CP violation and baryon asymmetry” [hep-ph/9312215]
[3] P. Huet and E. Sather, “Electroweak baryogenesis and standard model CP violation" [hep-ph/9404302]
[4] K. Fujikura, K. Harigaya, Y. Nakai and R. Wang “Electroweak-like Baryogenesis with New Chiral Matter” [arXiv:2103.05005]


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Last-modified: 2021-04-12 (月) 11:04:35 (284d)