セミナー 2019年

Pablo Soler, Institute for Theoretical Physics, University of Heidelberg

Swampland conjectures and some phenomenological applications

Meeting room 1, Kenkyu honkan 1F
An enormous amount of four dimensional effective field theories can be obtained from compactifications of string theory, forming a set known as the landscape of string theory. It has been suggested that, beyond this landscape, there exist consistent-looking effective field theories that cannot be embedded into UV complete theories of quantum gravity, in particular into string theory. They are said to belong to the swampland. In this talk, I will describe some of the conjectures that define the swampland and implications they have on phenomenology (e.g. dark matter, inflation and the cosmological constant).

Masazumi Honda, University of Cambridge

Quantum Black Hole Entropy from 4d Supersymmetric Cardy formula

Meeting room 3, Kenkyu honkan 1F, slides (kek.jp only)
I will talk about supersymmetric index of 4d N=1 supersymmetric theories on S^1xM_3 which counts supersymmetric states. In the first part, I will discuss a general formula to describe an asymptotic behaviour of the index in the limit of shrinking S^1 which we refer to as 4d (refined) supersymmetric Cardy formula. This part is based on arXiv:1611.00380 with Lorenzo Di Pietro. In the second part, I will apply this formula to black hole physics. I will mainly focus on superconformal index of SU(N) N=4 super Yang-Mills theory which is expected to be dual to type IIB superstring theory on AdS_5 x S^5. We will see that the index in the large-N limit reproduces the Bekenstein-Hawking entropy of rotating charged BPS black hole on the gravity side. Our result for finite N makes a prediction to the black hole entropy with full quantum corrections. The second part is based on arXiv:1901.08091.

Fumihiko Sugino, Institute for Basic Science

Study of highly entangled spin chains

Seminar room, Kenkyu honkan 3F, slides (kek.jp only)
Quantum entanglement is the most surprising feature of quantum mechanics. Ground states of quantum many-body systems typically exhibit the area law behavior in the entanglement entropy, which measures the amount of entanglement between a subsystem and the rest of the system. Recently, a class of solvable one-dimensional spin models with local interactions has been constructed, in which the ground state is expressed as a superposition of random walks, and has much larger entanglement entropy proportional to a square root of the volume. It seems to share some features of random geometry with matrix models. In this talk, I explain properties of these model and their implication to quantum gravity. In computation of the Renyi entropy for them, a new phase transition takes place in varying a parameter in the definition of the Renyi entropy.

Jung Chang, Chonnam National University

Forecast for Higgs boson self coupling measurement at the HL-LHC collider

Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
We perform the most up-to-date comprehensive signal-background analysis for the Higgs pair production in the $HH \rightarrow b \bar{b} \gamma\gamma$ channel at the HL-LHC collider. We simulate the signal processes with various values of Higgs boson self coupling $\lambda_{3H}/\lambda^{SM}_{3H}$ and all the standard-model background processes. We find that the Higgs boson self-coupling is constrained to $-1.5 < \lambda_{3H} < 8.1$ at $ 95\% $ confidence level after considering the uncertainties associated with the top-Yukawa coupling and the estimation of backgrounds. In this speech, we firstly review the cut-based analysis and introduce our recent improvements using Boosted Decision Trees(BDT).

Keita Nii, Institute for Theoretical Physics, University of Bern

Seiberg N-ality

Meeting room 1, Kenkyu honkan 1F

I will explain the low-energy dynamics of the 3d N=2 supersymmetric “chiral” SU(N) gauge theory, especially focussing on the understanding of the Coulomb branch of the moduli space of vacua (known as monopole operators). By correctly taking into account these operators, one can find a “simple” 3d Seiberg duality which relates two “simple” theories. As corollaries of this, I find s-confinement phases and Seiberg N-ality. This talk is based on Nucl.Phys. B939 (2019) 507-533.

Hayato Hirai, Osaka University

Conservation Laws from Asymptotic Symmetry and Subleading Charges in QED

Seminar room, kenkyu honkan 3F, slides (kek.jp only)
Recently, the asymptotic symmetry has been investigated in order to understand infrared physics better in QED. In particular, the memory effects and soft theorems turned out to be understood as consequences of the asymptotic symmetry. In this talk, I will start with the review of the triangle equivalences between the asymptotic symmetry, memory effects and soft theorems. Then, I will discuss our results about the charge conservation law associated with the asymptotic symmetry, physicalness of the symmetry in BRST formalism, and new conserved charge associated with the sub-leading soft theorem in massive scalar QED.

Masahiro Nozaki, RIKEN

Signature of quantum chaos in operator entanglement in 2d CFTs

Seminar room, Kenkyu honkan 3F, slides (kek.jp only)
We study operator entanglement measures of the unitary evolution operators of (1+1)-dimensional conformal field theories (CFTs), aiming to uncover their scrambling and chaotic behaviors. In particular, we compute the bi-partite and tri-partite mutual information for various configurations of input and output subsystems, and as a function of time. We contrast three different CFTs: the free fermion theory, compactified free boson theory at various radii, and CFTs with holographic dual. We find that the bi-partite mutual information exhibits distinct behaviors for these different CFTs, reflecting the different information scrambling capabilities of these unitary operators; while a quasi-particle picture can describe well the case the free fermion and free boson CFTs, it completely fails for the case of holographic CFTs. Similarly, the tri-partite mutual information also distinguishes the unitary evolution operators of different CFTs. In particular, its late-time behaviors, when the output subsystems are semi-infinite, are quite distinct for these theories. We speculate that for holographic theories the late-time saturation value of the tri-partite mutual information takes the largest possible negative value and saturates the lower bound among quantum field theories.

Kohei Kamada, RESCEU, The University of Tokyo

Primordial magnetic fields and their roles in particle physics and cosmology

Meeting room 3, Kenkyu honkan 1F, slides (kek.jp only)
Recent observations of TeV blazars by Fermi identified deficits of secondary GeV cascade photons. These observations can be explained by intergalactic magnetic fields, which may have a primordial origin. If the magnetic fields are helical and generated in the early Universe such as before the electroweak symmetry breaking, nontrivial interaction between (hyper)magnetic fields and other particles can cause some interesting and non negligible phenomena in the early Universe. In this talk, I will show that the baryon asymmetry can be generated by the chiral anomaly, and depending on the detail of electroweak cross over, baryon asymmetry is not completely washed out by the electroweak sphalerons. Thus, this mechanism can be responsible for the present baryon asymmetry of the Universe. If this mechanism is responsible for the present Universe, the BSM physics is needed for the generation of (hyper)magnetic fields but not for the baryogenesis. I will also discuss possible mechanism to generate such helical hypermagnetic fields suitable for the baryogenesis scenario.

松原隆彦, KEK


Room 346, 4 go-kan

Monika Blanke, Institute for Nuclear Physics (IKP), Karlsruhe Institute of Technology

Status of New Physics in Lepton Flavour Universality Violating B Decays

Seminar Room, Kenkyu honkan 3F
Recent data from LHCb and the B factories exhibit intriguing deviations from the Standard Model in B decay observables related to lepton flavour universality violation. I will review the current status of these anomalies and outline the possible diections in BSM model building to address them. I will then introduce a specific BSM model, which is based on the Pati-Salam gauge group in the 5-dimensional Randall-Sundrum spacetime.

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