Date/Place Mar. 27th (Wed.) (Informal) 16:30-17:30 / H711
Name Niko Koivunen (Helsinki)
Title Froggatt-Nielsen mechanism in a model with 331-gauge group (Slides)
Abstract The models with the gauge group SU(3)_c\times SU(3)_L\times U(1)_X (331-models) have been advocated to explain why there are three fermion generations in Nature. As such they provide partial understanding of the flavour sector. The hierarchy of fermion masses in the Standard Model is another puzzle which remains without compelling explanation. In this talk I present a model that incorporates Froggatt-Nielsen mechanism into a 331-model in order to explain both fundamental problems. It turns out that no new additional scalar representations are needed to take care of this. The 331-models thus naturally include explanations to both the number of fermion generations and their mass hierarchy. This talk is based on arXiv:1706.09463[hep-ph].


Date/Place Feb. 25th (Mon.) (Informal) 16:00-17:00 / H711
Name Igor Ivanov (IST, Lisbon)
Title Three-Higgs-doublet models: the broad picture and hidden gems (Slides)
Abstract Multi-Higgs-doublet models is a very popular class of New Physics models, conservative in assumptions but very rich in phenomenological and astroparticle consequences. For decades, the two-Higgs-doublet model was our main playground, but now many theorists look beyond two doublets. In this informal seminar I will first briefly overview this research activity and then, focusing on the three-doublet case, show a few intriguing examples.


Date/Place Jan. 29th (Tue.) 15:30-16:30 / H711
Name Takahiro Sagawa (U. of Tokyo)
Title Second law and eigenstate thermalization in isolated quantum many-body systems (Slides)
Abstract In recent years, the fundamental mechanism of thermalization of isolated many-body quantum systems has attracted renewed attentions, in light of quantum statistical mechanics, quantum information theory, and quantum technologies. In particular, it has been recognized that the eigenstate thermalization hypothesis (ETH) plays a crucial role in understanding the mechanism of thermalization, which states that even a single energy eigenstate is thermal if the system is quantum chaotic. In this talk, I will discuss our recent results on the second law of thermodynamics for pure quantum states [1]. In our setup, the entire system obeys unitary dynamics, where the initial state of the heat bath is not the Gibbs ensemble but a single energy eigenstate. Our proof is mathematically rigorous, and the Lieb-Robinson bound plays a crucial role. In addition, I will talk about our numerical result on large deviation analysis of the ETH [2], which directly evaluates the number of athermal energy eigenstates and validates the ETH. Our results would reveal a general scenario that thermodynamics emerges purely from quantum mechanics. [1] E. Iyoda, K. Kaneko, and T. Sagawa, Phys. Rev. Lett. 119, 100601 (2017). [2] T. Yoshizawa, E. Iyoda, and T. Sagawa, Phys. Rev. Lett. 120, 200604 (2018).


Date/Place Jan. 22nd (Tue.) 15:30-16:30 / H711
Name Shinji Takeda (Kanazawa U.)
Title QCD phase diagram (Slides)
Abstract It is known that the nature of finite temperature QCD phase transition depends on the number of quark flavors and quark masses. Such a situation is often pictorially summarized as the Columbia plot. There is an important and longstanding issue on the structure of the plot, namely the location of the critical line which separates the first order phase transition region from the cross-over region. In this talk, I will review and show some recent progresses on the issue by lattice QCD simulations. I will also address another issue how the Columbia plot is affected by the presence of finite quark density.


Date/Place Jan. 15th (Tue.) 15:30-16:30 / H711
Name Hosho Katsura (U. of Tokyo)
Title Topological order and zero modes in interacting Kitaev/Majorana chains (Slides)
Abstract In this talk, I will talk about a series of my work on a system of interacting spinless fermions in one (spatial) dimension. In the absence of interactions, the model reduces to the Kitaev chain, a paradigmatic model for topological superconductors. A signal of topological order there is the presence of zero-energy Majorana modes localized near the edges. I will argue that the exact (many-body) ground states can be obtained analytically even in the presence of interactions when the on-site potential is tuned to a particular function of the other parameters. The ground states obtained are two-fold degenerate and differ in fermionic parity. I will show that these ground states are unique and adiabatically connected to the ground states of the non-interacting Kitaev chain without gap closing, meaning that the model is in the same phase as the original Kitaev chain with topological order. If time allows, I will discuss an extension of the results to the spatially inhomogeneous case [3].

[1] H. Katsura, D. Schuricht, and M. Takahashi, Phys. Rev. B 92, 115137 (2015).
[2] K. Kawabata, R. Kobayashi, N. Wu, and H. Katsura, Phys. Rev. B 95, 195140 (2017).
[3] J. Wouters, H. Katsura, and D. Schuricht, Phys. Rev. B 98, 155119 (2018).


Date/Place Jan. 8th (Tue.) 15:30-16:30 / H711
Name Akihiro Ishibashi (Kinki U.)
Title The Quantum Null Energy Condition and its violation (Slides)
Abstract In this talk I will discuss the quantum null energy condition (QNEC) in curved spacetime. First, I will give a brief review on the (achronal) averaged null energy condition, its major role in spacetime physics, the quantum focusing conjecture, and the notion of QNEC. Then, I will examine the QNEC for a CFT in a wormhole spacetime by using AdS-CFT correspondence. Our bulk spacetime is a numerically constructed AdS black hole solution to the 3+1-dimensional vacuum Einstein equations with a 2+1-dimensional wormhole on its conformal boundary. By computing the IR-regularized entanglement entropy for a half-space anchored to the wormhole throat, it is shown that the QNEC can be violated around the throat. This indicates that IR-effects are crucial for QNEC. This talk is based on the joint work arXiv:1808.05192 with Kengo Maeda and Eric Mefford.


Date/Place Dec. 18th (Tue.) 15:30-16:30 / H711
Name Arindam Das (Osaka U.)
Title Right handed neutrinos: a roadmap from the energy to the intensity frontiers (Slides)
Abstract In this talk we will study the mass generation mechanisms of the Standard Model (SM) light neutrinos through the commonly known seesaw and inverse seesaw mechanisms which involve SM gauge singlet heavy Majorana right handed neutrinos. We fix the model parameters to reproduce the neutrino oscillation data and to satisfy other experimental constraints, assuming the typical flavor structure/s of these models and the different types of hierarchical light neutrino mass spectra. With the fixed parameters in this way, we analyze the heavy neutrino signal at the colliders. For completeness, we also consider a general parameterization for the model parameters by introducing an arbitrary orthogonal matrix, and the non-zero Dirac and Majorana phases. We perform parameter scan to identify an allowed parameter region which satisfies all experimental constraints. We find that in some cases, the heavy neutrino signal can be observed with a large statistical significance via different flavour charged lepton final states. We will also discuss about the significance of these right handed neutrinos in the intensity frontier beyond the collider searches.


Date/Place Dec. 11th (Tue.) 15:30-16:30 / H711
Name Masafumi Kurachi (Keio U.)
Title Topological objects in two Higgs doublet models (Slides)
Abstract In this talk, after a brief review of topological objects in field theory, I will discuss several types of topological objects appearing in two Higgs doublet models. Phenomenological impact of those objects will be also discussed.


Date/Place Dec. 5th (Wed.) 14:00-17:00 (Informal lecture) / H711
Name Holger Nielsen (Niels Bohr Institute)
Title Multiple point principle


Date/Place Dec. 5th (Wed.) 12:10-13:10 / H711
Name Holger Nielsen (Niels Bohr Institute)
Title Dark matter and its radiation X ray 3.55 keV (Slides)
Abstract We have long worked on a model for dark matter in which the particles of the dark matter have masses of the order of half a million tons. Indeed the dark matter consist of cm sized pearls with a density similar to that of white dwarf material. Using parameters originally - previous to the establishing of the X-ray with photon energy 3.55 keV supposed to come from dark matter - fitted to the appearance of Tunguska event occuring once every century, we already get order of magnitude not so badly both the rate of this X-ray radiation and the photon frequency, the 3.55 keV.


Date/Place Dec. 4th (Tue.) 15:30-16:30 / H711
Name Cen Zhang (IHEP, Beijing)
Title Positivity bounds on vector boson scattering (Slides)
Abstract Weak vector boson scattering (VBS) process is a sensitive probe of new physics effects in the electroweak symmetry breaking. Currently, experimental results at the LHC are interpreted in the effective field theory (EFT) approach, where possible deviations from the Standard Model in the quartic-gauge-boson couplings are described by 18 dimension-8 operators. By assuming that a UV completion exists, we derive a new set of theoretical constraints on the coefficients of these EFT operators, i.e. certain linear combinations of coefficients must be positive. These constraints imply that the current EFT approach to VBS has a large redundancy: only ∼3% of the full parameter space may correspond to a real UV completion. By excluding the unphysical region of the EFT parameter space, these constraints provide guidance for future VBS studies and measurements at the LHC.


Date/Place Dec. 3rd (Mon.) 16:30-17:30 (Informal) / H711
Name Valentin Tenorth (Max Planck Heidelberg)
Title Extended Dark Matter EFT (Slides)
Abstract The search for Dark Matter is one of the main tasks of modern particle physics, which is performed in "mono-X" searches at the LHC, indirect and direct detection experiments. I present a new framework in the language of effective field theory (EFT) to describe DM-SM interactions and combine experimental limits from nuclear energies at Direct Detection experiments to the TeV-scale at the LHC.To improve the high energy-validity of conventional DM EFTs a dynamical (pseudo-) scalar is added serving as mediator to the dark sector, represented by a fermion (or scalar), where richer new-physics sectors can be consistently included via higher-dimensional operators. The model is formulated in a gauge-invariant way and allows to confront classical Dark Matter observables with measurements of the Higgs sector.Interestingly the leading effects originate at dimension-five, allowing to capture them with a rather small set of parameters.Constraints on the parameter space arising from collider mono-X searches, the relic abundance, indirect and direct detection experiments are presented.The "model-independent" approach allows to apply the results to different UV-complete models such as 2HDM+a, extended fermion sectors, the NMSSM and composite mediators.In a (shorter) second part I discuss an approach to the SM flavor hierarchies and DM from the EW scale with a minimal new field content. Both the flavon and a pseudoscalar mediator to the Dark Sector arise from a combination of two flavor-charged Higgs Doublets. This leads to a predictive model with an interesting and rich phenomenology, which can be tested in different experiments in the near future.


Date/Place Nov. 27th (Tue.) 15:30-16:30 / H711
Name Kazuya Yonekura (Kyushu University)
Title Black hole information and Reeh-Schlieder theorem (Slides)
Abstract I will talk about implications of the Reeh-Schlieder theorem on the black hole information problem. In particular, I will argue that the Reeh-Schlieder theorem implies that “information” cannot be localized, and hence there is no well-defined concept of “information which is inside/outside event horizon”. Therefore, I claim that the black hole information problem is not well-formulated from the beginning.


Date/Place Nov. 22nd (Tue.) 15:30-16:30 / H711
Name Tomonori Ugajin (OIST)
Title Modular Hamiltonians of excited states, OPE blocks and emergent bulk fields
Abstract We study the entanglement entropy and the modular Hamiltonian of slightly excited states reduced to a ball shaped region in generic conformal field theories. We set up a formal expansion in the one point functions of the state in which all orders are explicitly given in terms of integrals of multi-point functions along the vacuum modular flow, without a need for replica index analytic continuation. We show that the quadratic order contributions in this expansion can be calculated in a way expected from holography, namely via the bulk canonical energy for the entanglement entropy, and its variation for the modular Hamiltonian. The bulk fields contributing to the canonical energy are defined via the HKLL procedure. In terms of CFT variables, the contribution of each such bulk field to the modular Hamiltonian is given by the OPE block corresponding to the dual operator integrated along the vacuum modular flow. These results do not rely on assuming large N or other special properties of the CFT and therefore they are purely kinematic.


Date/Place Nov. 15th (Thur.) 15:30-16:30 / H711
Name Hiroshi Suzuki (Kyushu University)
Title Lattice energy-momentum tensor from the gradient flow (Slides)
Abstract Because of its simple renormalization property, the so-called gradient flow can be used to define renormalized finite operators in gauge theory in a regularization independent way. This fact can be used to construct the energy-momentum tensor (EMT)—the Noether current associated with the translation invariance—in lattice gauge theory. I will explain the basic idea for this and present some recent activities in lattice numerical simulations on the basis of the gradient flow representation of the EMT.


Date/Place Nov. 13th (Tue.) 15:30-16:30 / H711
Name Goro Ishiki (University of Tsukuba)
Title Spherical transverse M5-branes from the plane wave matrix model (Slides1 Slides2)
Abstract We consider the matrix theoretical description of transverse M5-branes in M-theory on the 11-dimensional maximally supersymmetric pp-wave background. We apply the localization to the plane wave matrix model (PWMM) and show that the transverse spherical fivebranes with zero light cone energy in M-theory are realized as the distribution of low energy moduli of the SO(6) scalar fields in PWMM.


Date/Place Nov. 6th (Tue.) 15:30-16:30 / H711
Name Nobuhito Maru (Osaka City University)
Title Dark matter in gauge-Higgs unification (Slides)
Abstract We propose two Dark Matter (DM) scenarios in the context of 5D gauge-Higgs Unification (GHU) model. The first one is a fermion DM, the other is an SU(2)L doublet vector DM. We discuss their physical implications.


Date/Place Oct. 23th (Tue.) 15:30-16:30 / H711
Name Hiroyuki Tashiro (Nagoya University)
Title Cosmology with the measurements of redshifted 21 cm signals (Slides)
Abstract Observations of cosmological 21 cm signals are expected to provide a new window to the universe. The observed signals are sensitive to the structure formation, the thermal evolution and the expansion history of the universe. Recently the first detection of the cosmological 21 cm signal around the redshift 20 was claimed by the EDGES collaboration. In this talk, I will give the theoretical introduction of cosmological 21 cm observations. Reviewing the EDGES result, I will also discuss its application to cosmological problems including the dark matter modelling.


Date/Place Oct. 16th (Tue.) 15:30-16:30 / H711
Name Yu Hamada (Kyoto University)
Title Axial U(1) current in Grabowska and Kaplan’s formulation (Slides)
Abstract Recently, Grabowska and Kaplan suggested a non-perturbative formulation of a chiral gauge theory (arXiv: 1511.03649). This formulation consists of the conventional domain-wall fermion and a gauge field that evolves by the gradient flow from one domain wall to the other. In this talk, I will briefly review their formulation and some related works. I will also discuss the QCD axial U(1) current in the formulation. It is found that the naive definition of the current does not reproduce the axial anomaly because the current includes a contribution from the bulk. I will suggest the correct definition of the current. This talk is based on the collaboration with Hikaru Kawai (arXiv: 1705.01317).


Date/Place Oct. 10th (Wed.) 12:10-13:10 / H711
Name Johannes Braathen (Osaka University)
Title Automating Higgs precision calculations (Slides)
Abstract The Standard Model-like Higgs boson provides an excellent setting for the indirect search of New Physics, through the precise study of its properties. In particular the Higgs boson mass is now measured with an astonishing precision -- of the order of 0.1% -- while being predicted in some models of Beyond the Standard Model (BSM) Physics, such as supersymmetric (SUSY) models. This motivates high-precision calculations of the Higgs mass(es), but at the same time raises the question of how best to proceed to be able to study a wide range of models. In this talk, I will present a possible option in this context, namely automation: i.e. to perform the difficult calculation of higher-order corrections to a given observable -- here masses -- once for a general renormalisable theory, and then to apply these results to the particular model(s) one may want to study (this latter step being simple to automatise). In a first part of this presentation, I will consider fixed-order calculations of Higgs masses in generic theories. For these, the current state-of-the-art consists of two-loop analytic expressions obtained in the Landau gauge, and which are now available in public tools such as SARAH/SPheno. However, until recently, these calculations were plagued by the so-called "Goldstone boson catastrophe" (GBC), a case of infrared divergences due to tachyonic Goldstone boson running masses. After explaining how the GBC appears, I will discuss the recent solution found for general renormalisable models and its implementation in SARAH. I will then illustrate new results for Higgs masses, focusing in particular on how they allow to extract Lagrangian couplings from the scalar mass spectrum at two loops in the context of non-SUSY extensions of the SM. A second part will be devoted to the Effective Field Theory (EFT) approach to Higgs mass calculations, and more precisely to recent work on the one-loop matching of the scalar quartic couplings between two generic theories. Finally, I will discuss the ongoing calculation of two-loop corrections to Higgs trilinear couplings in models with extended Higgs sectors.


Date/Place Oct. 9th (Tue.) 15:30-16:30 / H711
Name Po-Yen Tseng (Kavli IPMU)
Title Muon g-2 and rare top decays in variant axion models (Slides)
Abstract The variant axion models(VAM) offer a solution for the strong CP problem without the domain wall issue. We consider the up-specific VAM and examine their compatibility wit the muon g-2 anomaly and constraints from lepton universality, flavor observables, and top quark measurements. We find the preferred parameter space requires light pseudo-scalar (A) about 15 GeV and tan\beta~40. Moreover, we find non-zero mixing angle among the right-handed up-quarks has no conflict with any observable, as long as this mixing angle is smaller than 0.06. This gives rise to sizable top flavor changing decay, t → uA or cA, and become a smoking gun signal at LHC.


Date/Place Oct. 2th (Tue.) 15:30-16:30 / H711
Name Koji Umemoto (YITP)
Title Entanglement of Purification in Holography and its Multipartite Generalization (Slides)
Abstract It has been more than 10 years since a connection between quantum information theory and quantum gravity was found in the context of AdS/ CFT correspondence. There it was conjectured that the entanglement entropy in holographic CFTs is equal to the minimal geometrical area of certain codimention-2 surfaces in the bulk AdS. This is now called Ryu- Takayanagi or holographic entanglement entropy formula and has passed substantial tests. Since the entanglement entropy represents an amount of quantum entanglement for pure states, this formula motivate us to investigate the potential relationship between boundary entanglement and bulky geometry.
However, one problem here is that one can not use the entanglement entropy as a measure of entanglement for mixed states: the entanglement entropy loose its meaning of “entanglement” for mixed states and becomes just a von Neumann entropy of considered subsystem. Such mixed states naturally appear in AdS/CFT e.g. when one considers bipartite subsystems on the boundary, or black hole geometry itself is also mixed.
In this seminar, we talk about a generalization of the holographic entanglement entropy formula which is applicable for mixed states. We propose that the entanglement of purification, which is a generalization of entanglement entropy for mixed states capturing both quantum entanglement and classical correlations, has a gravitational counterpart expressed by a certain minimal area of codimension-2 surface in the entanglement wedge. We show that known properties of entanglement of purification are indeed satisfied by the conjectured holographic counterpart, and also give a heuristic explanation why this relation happens based on the tensor network description.
On the other hand, another problem is that in multipartite systems (such as 3 qubits) we have to deal with multipartite entanglement to know the detailed structure of quantum states. Again the entanglement entropy can not be used for this purpose. Then we also generalize the holographic entanglement of purification conjecture to multipartite setups and test its validity. We define a multipartite generalization of entanglement of purification and that of holographic counterpart, and then prove their properties independently. We confirm that these two quantity indeed share all the properties we concerned. These agreements support the multipartite (including bipartite) holographic entanglement of purification conjecture.


Date/Place Aug. 21st (Tue.) (Informal) 15:30-16:30 / H711
Name Yuta Hamada (U. of Wisconsin, KEK)
Title Weak Gravity Conjecture from Unitarity
Abstract Weak Gravity Conjecture provides the lower bound on the Abelian gauge coupling in the theory of quantum gravity. In this talk, I will show that, under several assumptions, a class of weak gravity conjecture follows from the unitarity of the quantum field theory.


Date/Place Jul. 31th (Tue.) 15:30-16:30 / H711
Name Teruaki Suyama (Titech)
Title Primordial black holes in the era of gravitational wave astronomy (Slides)
Abstract Black holes might have formed in the very early universe before the big bang nucleosynthesis. Those black holes, known as primordial black holes(PBHs), behave as dark matter, and there are a lot of studies about whether PBHs can explain all dark matter or not. The recent discovery of binary black holes by LIGO has led to a resurgence of the PBH hypothesis. In this talk, I will present my recent study which showed a possibility that LIGO black holes are PBHs. I will also discuss about how to test the PBH hypothesis by future gravitational wave observations.


Date/Place Jul. 30th (Mon.) (Informal) 16:00-17:00 / H711
Name Kenji Kadota (IBS)
Title Particle cosmological probes on the light dark matter (Slides)
Abstract A few examples for the light dark matter will be discussed with an emphasis to illustrate the complementarity between the particle physics and cosmology probes.


Date/Place Jul. 24th (Tue.) 15:30-16:30 / H711
Name Masazumi Honda (Weizmann Institute of Science)
Title Introduction to Resurgence and Complex saddle point analysis (Slides)
Abstract Resurgence is a technique to resum asymptotic perturbative series which has often reproduced exact results in various problems. This talk will focus on applications of resurgence for weak coupling perturbative series of quantities represented by (path) integrals. I will discuss that in this type of problems, we have to perform saddle point analysis "seriously". Namaly, we need to take care of global steepest decsents (Lefschetz thimble) and complex saddle points which are not on original (path) integral contour. I will demonstrate these points in terms of very simple examples. I will also briefly mention recent applications of Lefschetz thimble to various problems.


Date/Place Jul. 18th (Wed.) (Informal) 13:30- / H711
Name Shinji Hirano (Wits & Yukawa Inst.)
Title Airy Function and 4d Quantum Gravity
Abstract We study 4d quantum gravity with negative cosmological constant in the minisuperspace approximation and compute the partition function for the S^3 boundary geometry. In this approximation scheme the path integrals become dominated by a class of asymptotically AdS "microstate geometries." Despite the fact that the theory is pure Einstein gravity without supersymmetry, the result precisely reproduces, up to higher curvature corrections, the Airy function in the S^3 partition function of the maximally supersymmetric Chern-Simons-matter (CSM) theory which sums up all perturbative 1/N corrections. We also show that this can be interpreted as a concrete realization of the idea that the CFT partition function is a solution to the Wheeler-DeWitt equation as advocated in the holographic renormalization group. Furthermore, the agreement persists upon the inclusion of a string probe and it reproduces the Airy function in the vev of half-BPS Wilson loops in the CSM theory.


Date/Place Jul. 17th (Tue.) 15:30-16:30 / H711
Name Kohtaro Tamaoka(Osaka University)
Title Towards Entanglement of Purification for Conformal Field Theories (Slides)
Abstract We argue that the entanglement of purification for two dimensional holographic CFT can be obtained from conformal blocks with internal twist operators. First, we explain our formula from the view point of tensor network model of holography. Then, we apply it to bipartite mixed states dual to subregion of AdS3 and the static BTZ blackhole geometries. The formula in CFT agrees with the entanglement wedge cross section in the bulk, which has been recently conjectured to be equivalent to the entanglement of purification.


Date/Place Jul. 17th (Tue.) (Informal) 13:15- / H711
Name Masazumi Honda (Weizmann Institute of Science)
Title Cardy Formula for 4d SUSY Theories and Localization
Abstract We study 4d N=1 supersymmetric theories on a compact Euclidean manifold of the form S^1xM_3. Partition functions of gauge theories on this background can be computed using localization, and explicit formulas have been derived for different choices of the compact manifold M_3. Taking the limit of shrinking S^1, we present a general formula for the limit of the localization integrand, derived by simple effective theory considerations, generalizing the result of arXiv:1512.03376. The limit is given in terms of an effective potential for the holonomies around the S^1, whose minima determine the asymptotic behavior of the partition function. If the potential is minimized in the origin, where it vanishes, the partition function has a Cardy-like behavior fixed by Tr(R), while a nontrivial minimum gives a shift in the coefficient. In all the examples that we consider, the origin is a minimum if Tr(R)≤0.


Date/Place Jul. 10th (Tue.) 15:30-16:30 / H711
Name Kei Yagyu (Seikei University)
Title SUSY VS Compositeness: 2HDMs tell the story (Slides)
Abstract Although a Higgs boson was discovered at the LHC, we still do not know what is the Nature of the Higgs boson. So far, two big paradigms have been discussed to clarify the Nature of the Higgs boson, namely, supersymmetry and compositeness, where Higgs physics is described by weak and strong dynamics, respectively. Both of these scenarios predict a 2-Higgs doublet model (2HDM) as a low energy effective theory. In this talk, we discuss how we can determine the true dynamics at a TeV scale by focusing on differences in various properties of the 2HDM.


Date/Place July. 3th (Tue.) 15:30-16:30 / H711
Name Takao Suyama (KEK)
Title \theta=\pi in SU(N)/Z_N Theory (Slides)
Abstract In SU(N) gauge theory, it is argued recently that there exists a "mixed anomaly" between the CP symmetry and the 1-form ZN symmetry at θ=π, and the anomaly matching requires CP to be spontaneously broken at θ=π if the system is in the confining phase. In this paper, we elaborate on this discussion by examining the large volume behavior of the partition functions of the SU(N)/ZN theory on T4 a la 't Hooft. The periodicity of the partition function in θ, which is not 2π due to fractional instanton numbers, suggests the presence of a phase transition at θ=π. We propose lattice simulations to study the distribution of the instanton number in SU(N)/ZN theories. A characteristic shape of the distribution is predicted when the system is in the confining phase. The measurements of the distribution may be useful in understanding the phase structure of the theory.


Date/Place Jun. 26th (Tue.) 15:30-16:30 / H711
Name Yoshio Kikukawa (Univ. of Tokyo)
Title On the gauge invariant path-integral measure for the overlap Weyl fermoins in 16 of SO(10)
Abstract We consider the lattice formulation of SO(10) chiral gauge theory with left-handed Weyl fermions in the sixteen dimensional spinor representation (16) within the framework of the Overlap fermion/the Ginsparg-Wilson relation. We define a manifestly gauge-invariant path-integral measure for the left-handed Weyl field using all the components of the Dirac field, but the right-handed part of which is just saturated completely by inserting a suitable product of the SO(10)-invariant 't Hooft vertices in terms of the right-handed field. The measure possesses all required transformation properties under lattice symmetries and the induced effective action is CP invariant.


Date/Place Jun. 22nd (Fri.) 12:10-13:10 / H711
Name Hermann Nicolai (Max Planck Institute)
Title The Conformal Standard Model (Slides)
Abstract The Conformal Standard Model (CSM) is a minimal extension of the Standard Model of Particle Physics based on the assumed absence of large intermediate scales between the TeV scale and the Planck scale, which incorporates only right-chiral neutrinos and a new complex scalar in addition to the usual SM degrees of freedom, but no other features such as supersymmetric partners. In this talk I will present an overview and argue that all outstanding issues of particle physics proper can in principle be solved ‘in one go’ within this framework. The main testable prediction of the model is a new and almost sterile scalar boson that would manifest itself as a narrow resonance in the TeV region.


Date/Place Jun. 12th (Tue.) 15:30-16:30 / H711
Name Motoi Endo (KEK)
Title Revisiting TeV-scale SUSY (Slides)
Abstract Although no new particles have been discovered in the LHC experiments, SUSY has been one of the most attractive scenarios of physics beyond the SM. In this talk, we overview the status and prospects of SUSY in a TeV scale. In particular, we will show that some of the flavor anomalies are (still) explained well by the scenarios without conflicting with the LHC and other constraints.


Date/Place Jun. 8th (Fri.) 13:30-14:30 / H711
Name Takeo Moroi (Univ. of Tokyo)
Title Stability of Electroweak Vacuum in the Standard Model and Beyond (Slides)
Abstract I will discuss recent progresses of the calculation of the decay rate of the electroweak vacuum in the standard model. I will also discuss how extra fermions may affect the stability of the electroweak vacuum.


Date/Place May. 29th (Tue.) 15:30-16:30 / H711
Name Shoji Hashimoto (KEK)
Title Quark-hadron duality and lattice QCD
Abstract Quark-hadron duality is a basic assumption which many perturbative QCD calculations rely on. There are plausible arguments about why it is valid, but only at a qualitative level. We propose a set of quantities for which quantitative and non-perturbative calculation is possible using lattice QCD. A well-known example is related to the R-ratio of e+e- scattering. A primary target of the method discussed in this talk is the inclusive decays of B mesons. We discuss on how one can calculate its decay rate or some related quantities.


Date/Place May. 23th (Wed.)(Informal) 12:10-1:10 / H711
Name Janusz Rosiek (University of Warsaw)
Title Decay of Higgs boson to photons in the Standard Model Effective Field Theory (Slides)
Abstract Potential effects of yet undiscovered New Physics can be universally parametrized in terms of the so-called SM Effective Field Theory, defined as the Standard Model extended with all gauge-invariant operators of higher dimensions constructed of the SM fields. I will discuss a consistent setup for the perturbative calculations in such a complicated (non-renormalizable) model, including derivation of the Feynman rules in terms of the physical fields and quantization of the theory in the R_xi gauges. Then, as an application I will present the calculation of the radiative decay of Higgs boson into 2 photons in SMEFT.


Date/Place May. 22th (Tue.) 15:30-16:30 / H711
Name Toshifumi Noumi (Kobe Univ.)
Title Weak Gravity Conjecture and Infrared Consistency (Slides)
Abstract As is captured by the word “string landscape,” an almost infinite number of low-energy effective theories may be described in the string theory framework. However, recent studies have revealed that there exist a certain class of consistent-looking IR effective theories which are not realized in string theory, or more generally in a consistent UV theory of quantum gravity. Such theories are said to live in the “swampland” and clarifying the boundaries of landscape and swampland is an important issue in both the theoretical and phenomenological contexts. In the first half of this talk, I will review a typical example for such a criterion called the Weak Gravity Conjecture and its phenomenological implications. In the latter half, I will discuss its possible connection to other QFT principles such as unitarity. In particular, I will introduce our new proposal which we call the Tower Weak Gravity Conjecture based on the recent work arXiv:1802.04287.


Date/Place May. 15th (Tue.) 15:30-16:30 / H711
Name Tatsuma Nishioka (Univ. of Tokyo)
Title OPE for Conformal Defects and Holography (Slides)
Abstract We study the operator product expansion(OPE) for scalar conformal defects of any codimension in CFT. The OPE for defects is decomposed into “defect OPE blocks”, the irreducible representations of the conformal group, each of which packages the contribution from a primary operator and its descendants. We use the shadow formalism to deduce an integral representation of the defect OPE blocks. They are shown to obey a set of constraint equations that can be regarded as equations of motion for a scalar field propagating on the moduli space of the defects. By employing the Radon transform between the AdS space and the moduli space, we obtain a formula of constructing an AdS scalar field from the defect OPE block for a conformal defect of any codimension in a scalar representation of the conformal group, which turns out to be the Euclidean version of the HKLL formula. We also introduce a duality between conformal defects of different codimensions and prove the equivalence between the defect OPE block for codimension-two defects and the OPE block for a pair of local operators.


Date/Place May. 8th (Tue.) 15:30-16:30 / H711
Name Sugumi Kannno (Osaka Univ.)
Title Quantum entanglement between bubble universes (Slides)
Abstract In de Sitter space where the universe expands exponentially, any two of mutually separated regions eventually become causally disconnected. This is most conveniently described by spanning open universe coordinates on two open charts in de Sitter space. Recently, Maldacena and Pimentel showed that the entanglement entropy of a free massive scalar field between two open charts is non-vanishing. This result shows that two causally disconnected regions in de Sitter space are entangled. I extend the calculation of Maldacena and Pimentel to the case where a bubble wall is present between the two open charts. This can be thought of as a model of pair creation of bubble universes in de Sitter space. I will discuss the effect of the bubble wall on the entanglement entropy between the bubble universes.


Date/Place Apr. 24th (Tue.) 15:30-16:30 / H711
Name Chen Zhang (NCTS)
Title Simplest Little Higgs Revisited: Hidden Mass Relation, Unitarity and Naturalness (Slides)
Abstract In this talk, I will present an analysis of the scalar potential of the Simplest Little Higgs (SLH) model in an approach consistent with the spirit of continuum effective field theory (CEFT). A hidden mass relation is obtained relating the pseudo-axion mass and top partner mass, serving as a crucial test of the SLH mechanism. I also propose a strategy of analyzing the fine-tuning problem consistent with the spirit of CEFT and apply it to the SLH. The scalar potential and fine-tuning analysis strategies investigated here should also be applicable to a wide class of Little Higgs and Twin Higgs models, which may reveal interesting relations as crucial tests of the related electroweak symmetry breaking mechanism and provide a new perspective on assessing their degree of fine-tuning.


Date/Place Apr. 17th (Tue.) 15:30-16:30 / H711
Name Yohei Ema (KEK)
Title Flaxion and its SUSY extension (Slides)
Abstract In this talk, we propose a minimal extension of the standard model which includes only one additional complex scalar field, flavon, with flavor-dependent global U(1) symmetry. It not only explains the hierarchical flavor structure in the quark and lepton sector (including neutrino sector), but also solves the strong CP problem by identifying the CP-odd component of the flavon as the QCD axion, which we call flaxion. Furthermore, the flaxion model solves the cosmological puzzles in the standard model, i.e., origin of dark matter, baryon asymmetry of the universe, and inflation. We also discuss a supersymmetric extension of this model, paying a particular attention to dynamics of an additional scalar flat direction in the early universe.


Date/Place Apr. 11th (Wed.) (Informal) 12:10 / H711
Name Ryo Nagai (Tohoku University)
Title Roles of perturbative unitarity in extended Higgs scenarios (Slides)
Abstract One of the important roles of the SM Higgs boson is to keep WW scattering amplitudes perturbatively unitary in high energy limit. However, once the Higgs coupling deviates from the SM prediction, the perturbative unitarity might be broken down at the certain energy scale. In order to maintain the perturbative unitarity with anomalous higgs coupling in high energy limit, we need new particle(s) whose couplings are tuned to cancel the bad behavior of WW scattering amplitudes. The required conditions are called “unitarity sum rules”. The sum rules tell us nontrivial relationship between the properties of new particles/phenomena and the low-energy observables such as the 125GeV signal strengths (coupling strengths). In this talk, we discuss the implications of the unitarity sum rules and apply the sum rules to investigate physics beyond the standard model.


Date/Place Apr. 4th (Wed.) (Informal) 14:30-15:30 / H711
Name Ryoutaro Watanabe (Montreal U.)
Title Does complete set of data still prefer the B anomalies?
Abstract In this talk, I will show my ongoing work regarding new physics to accommodate the anomalies in b -> s mu mu and b -> c tau nu which have been standing on these days. So far, there are many papers for this topic and they concluded that U1 (singlet vector type of) leptoquark could explain the two simultaneously. In our work, we put a complete set of observables relevant for the above explanation and gives a fit analysis. As a result, we see what kind of patterns of LQ couplings are favored, which could be a guideline when one constructs a UV completed model to accommodate the B anomalies.