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Tomohiro Matsuda

Publications and source records attributed to Tomohiro Matsuda.

At least 91 records · Page 5Linked to original sources
arXiv2003

Thermal hybrid inflation in brane world

In conventional scenario of thermal inflation, the requirement that the reheating temperature must be larger than the temperature of the nucleosynthesis puts a lower bound on the mass of the inflaton field. At the same time, the mass of the inflaton field and the height of the potential during thermal inflation are intimately related. With these conditions, the conventional models for thermal inflation are quite restricted. Naively, one can expect that the above constraints may be removed if thermal inflation is realized within the setups for hybrid inflation. In this paper we show why it is difficult to construct hybrid models for thermal inflation within conventional supergravity, and then show a successful example in models for the braneworld. Our mechanism is based on the idea of non-tachyonic brane inflation.

hep-ph↗
arXiv2003

Hybridized Affleck-Dine baryogenesis

We propose a novel scenario for Affleck-Dine baryogenesis in the braneworld, considering the hybrid potential for the Affleck-Dine field. Destabilization of the flat direction is not due to the Hubble parameter, but is induced by a trigger field. The moduli for the brane distance plays the role of the trigger field. Q-balls are unstable in models with large extra dimensions.

hep-ph↗
arXiv2003

Non-tachyonic brane inflation

We consider non-tachyonic hybrid inflation in the context of the braneworld cosmology. When one considers models for brane inflation, hybrid inflation is a natural consequence of the tachyon condensation if it appears at the end of inflation. In this case, however, reheating is a difficult problem due to the peculiar properties of the tachyon. In this paper we show some models for brane inflation where a new type of hybrid inflation is realized due to the localized matter fields. The obvious advantage of our scenario is successful reheating, which is due to the potential that is localized on the brane. The serious problem of the loop correction is also avoided.

hep-ph↗
arXiv2002

Kaluza-Klein modes in hybrid inflation

When one constructs specific models with the fundamental scale as low as the TeV scale, there arise many difficulties. In this paper we examine the hybrid inflation due to bulk scalar fields, which has been proposed to solve the problem of fine-tuning in producing density perturbations. We find that the Kaluza-Klein modes play significant roles, which enhance the speed of the phase transition and alter the reheating process. We also argue that a lower bound must be put to the fundamental scale, in order to construct the successful hybrid inflation due to the bulk scalar fields.

hep-ph↗
arXiv2002

Activated Sphalerons and Large Extra Dimensions

We present a new scenario for the baryon number violation that may take place in models with large extra dimensions. Our idea is interesting because leptogenesis with a low reheating temperature requires an alternative source of the B+L violation to convert the produced leptons into baryons. If one considers a model with an intermediate compactification radius, the reheating temperature may be allowed to become higher than the critical temperature of the conventional electroweak phase transition. Our mechanism is still important in this case, because it provides the phase boundary, which is an essential ingredient of the electroweak baryogenesis.

hep-ph↗
arXiv2002

Baryon number violation, baryogenesis and defects with extra dimensions

In generic models for grand unified theories(GUT), various types of baryon number violating processes are expected when quarks and leptons propagate in the background of GUT strings. On the other hand, in models with large extra dimensions, the baryon number violation in the background of a string is not trivial because it must depend on the mechanism of the proton stabilization. In this paper we argue that cosmic strings in models with extra dimensions can enhance the baryon number violation to a phenomenologically interesting level, if the proton decay is suppressed by the mechanism of localized wavefunctions. We also make some comments on baryogenesis mediated by cosmological defects. We show at least two scenarios will be successful in this direction. One is the scenario of leptogenesis where the required lepton number conversion is mediated by cosmic strings, and the other is the baryogenesis from the decaying cosmological domain wall. Both scenarios are new and have not been discussed in the past.

hep-ph↗
arXiv2002

Enhanced baryon number violation due to cosmological defects with localized fermions along extra dimension

We propose a new scenario of baryon number violation in models with extra dimensions. In the true vacuum, baryon number is almost conserved due to the localization mechanism of matter fields, which suppresses the interactions between quarks and leptons. We consider several types of cosmological defects in four-dimensional spacetime that shift the center of the localized matter fields, and show that the magnitudes of the baryon number violating interactions are well enhanced. Application to baryogenesis is also discussed.

hep-ph↗
arXiv2002

Affleck-Dine baryogenesis after thermal brane inflation

We propose a new scenario of Affleck-dine baryogenesis in the context of theories with large extra dimensions. In this paper we consider baryogenesis after thermal brane inflation and show how our mechanism works. We specifically consider models in which supersymmetry is broken at the distant brane.

hep-ph↗
arXiv2002

Affleck-Dine baryogenesis in the local domain

For Affleck-Dine baryogenesis to proceed, there must have been two types of phase transitions. One is the destabilized-stabilized phase transition of the flat direction, which is in general induced by the Hubble parameter. The other is the phase transition related to the A-term, which induces the misalignment of the relative phase of the flat direction. In the conventional Affleck-Dine baryogenesis they are supposed to start almost simultaneously. Of course these phase transitions can take place separately, but the latter must not be later than the former because the phase transition of the A-term can not produce any baryon number when there is no condensate of the relative charge. In this paper we try to construct models where the original idea of Affleck-Dine baryogenesis is realized in a different way. We show examples in which the local domain of the false vacuum with the required condensate is formed after inflation and collapses in a safe way so that the domain wall problem is avoided. We also show examples where the phase transition of the A-term starts before the decay of the condensate. As in the conventional Affleck-Dine mechanism, the phase transition of the A-term produces baryon number in the local domain of the condensate. We construct scenarios where our mechanism produces sufficient baryon asymmetry of the Universe.

hep-ph↗
arXiv2001

Electroweak baryogenesis mediated by locally supersymmetry-breaking defects

We consider the scenario of electroweak baryogenesis mediated by cosmological defect in models of supersymmetry breaking. When the effective electroweak breaking scale is raised in the defect configuration, the mechanism of electroweak baryogenesis works at a higher energy scale. The baryon charge produced by the mechanism is captured in the defect, protected from sphalerons and then released when the defect decay.

hep-ph↗
arXiv2001

Electroweak baryogenesis and hierarchy

We consider the scenario of electroweak baryogenesis mediated by cosmological defects in a model of extra dimension. We consider the domain wall on the brane in higher-dimensional theories.The electroweak breaking scale is suppressed and the sphaleron interaction is activated in the false vacuum.

hep-ph↗
arXiv2000

Weak Scale Inflation and Unstable Domain Walls

Cosmlogical domain walls produced during phase transition are expected to collapse on a cosmologically safe timescale if Vilenkin's condition is satisfied. We show that the decaying processes of these unstable domain walls should be changed significantly if weak scale inflation takes place. The usual condition for the safe decay of the cosmological domain wall must be changed, depending on their scales and interactions. As a result, the energy scales and explicit breaking terms of such walls must satisfy severe requirements. We also make a brief comment on cosmological structure formation.

hep-ph↗
arXiv1999

On Superpotential and BPS domain wall in SQCD and MQCD

We examine the decoupling properties of the N=2 SQCD vacua when the adjoint mass term is turned on and then the N=1 limit is taken. The BPS domain wall tension in N=1 MQCD and SQCD is also examined. The correspondence of the MQCD integrals with the superpotential and the gaugino condensate is shown.

hep-th↗
arXiv1998

On the cosmological domain wall problem in supersymmetric models

Many models for dynamical supersymmetry breaking have the domain wall solution of the Kovner-Shifman type and therefore contain the potential cosmological domain wall problem.We show that the degeneracy of the vacua is lifted in any model in which the cosmological constant is fine-tuned to zero through an explicit $Z_{n}^{R}$ symmetry breaking constant in the superpotential. In this respect, we do not have to add unnatural non-renormalizable terms which explicitly break the symmetry. We also discuss the conditions for the safe decay of the walls for several concrete examples.

hep-ph↗
arXiv1998

A natural solution to the $μ$-problem in dynamical supergravity model

The Higgs mixing term coefficient $μ$ is calculated in the supersymmetric theory which possesses a non-anomalous $U(1)_{R}$ symmetry in the limit of global supersymmetry. In this model, supersymmetry is assumed to be broken by gaugino condensation in the hidden sector when the supergravity effects are turned on. The soft breaking terms in the visible sector and the $μ$ term of order the weak scale are produced in a simple manner.

hep-ph↗
arXiv1997

Successful D-term Inflation with moduli

We examine a natural extension of D-term inflation and construct a successful model. General type of the D-term potential is shown to produce successful inflation with appropriate COBE normalization. The effect of the dilaton shift at the inflation period is taken into account.

hep-ph↗
arXiv1997

Large N expansion in global and local supersymmetric theories

A systematic study of large N expansion in supersymmetric theories are given. Supersymmetric O(N) non-linear sigma model in two and three dimensions, massless and massive supersymmetric QCD with $N_{f}<N_{c}-1$ and supergravity models are analyzed in detail. Our main motivation is to discuss how the previously studied mechanism for dynamical generation of gaugino condensation and superpotential is realized in the framework of large N expansion.

hep-ph↗