arXiv subjects

Mitsuo J. Hayashi

Publications and source records attributed to Mitsuo J. Hayashi.

12 recordsLinked to original sources

arXiv2010

Dilatonic Inflation, Gravitino and Reheating in Modified Modular invariant Supergravity

A new modified string-inspired modular invariant supergravity model is proposed and is applied to realize the slow roll inflation in Einstein frame, so that the model explains WMAP observations very well. Gravitino mass and their production rate from scalar fields are estimated at certain values of parameters in the model. Seven cases of parameter choices are discussed here, among which some examples show the possibility of observation of gauginos by LHC experiments, which will give some hints of identity of dark matters. The reheating temperature, which is estimated by the stability condition of Boltzmann equation by using the decay rates of the dilaton $S$ into gauginos, is lower than the mass of gravitino. Therefore no thermal reproduction of gravitinos happens. The ratio between the scalar and tensor power spectrum is predicted to be almost the same for the seven cases under study, and its value $r \sim 6.8 \times 10^{-2}$ seems in the range possibly observed by the Planck satellite soon. The plausible supergravity model of inflation, which will be described here, will open the hope to construct a realistic theory of particles and cosmology in this framework, including yet undetected objects.

hep-ph↗

arXiv2010

Inflation, Gravitino and Reheating in Modified Modular invariant Supergravity

A new modified string-inspired modular invariant supergravity model is proposed and is applied to realize the slow roll inflation in Einstein frame. Because inflation deals with Planck scale physics, the dilaton can be a strong candidate for identification with the inflaton. The model we used, cleared the $η$-problem and negative energy problem of potential at stable point, and appeared to predict successfully the values of observations at the inflation era. We proved that the model explains WMAP observations appropriately. Moreover, a mechanism of SSB and Gravitino production just after the end of inflation is investigated. We have obtained power spectrum of the density perturbation as $\mathcal{P_R}_* \sim 2.438 \times 10^{-9}$ and the scalar spectral index as $n_{s*}\sim 0.9746$ and its tilt as $α_{s*}\sim -4.3 \times 10^{-4}$. The ratio between scalar power spectrum and tensor is predicted as $r\sim 6.8 \times 10^{-2}$, a prediction which seems in the range possibly observed by the Planck satellite soon. The gravitino mass and their production rate from scalar fields are estimated at certain values of parameters in the model. The reheating temperature is estimated by the stability condition of Boltzmann equation by using the decay rate of the dilaton S into gauginos as $T_R({\rm gaugino}) = 3.88 \times 10^{7} \,\, {\rm GeV}$. Though only one example of parameter choices has been discussed here, the other seven candidates of parameter choices that are compatible with WMAP data have already been found by the authors. Some of the examples show that the gauginos can be observed by LHC experiments. The plausible supergravity model of inflation which here we described will open the hope to construct a realistic theory of particle theory and cosmology in this framework.

hep-ph↗

arXiv2010

Supersymmetry Breaking and Gravitino Production after Inflation in Modular Invariant Supergravity

By using a string-inspired modular invariant supergravity, which was proved well to explain WMAP observations appropriately, a mechanism of supersymmetry breaking (SSB) and Gravitino Production just after the end of inflation are investigated. Supersymmetry is broken mainly by F-term of the inflaton superfield and the Goldstino is identified to be inflatino in this model, which fact is shown numerically. By using the canonically normalized and diagonalized scalars, the decay rates of these fields are calculated, for both the $T$ and $Y$ into gravitinos. Non-thermal production of gravitinos is not generated from the inflaton (dilaton), since the inflaton mass is lighter than gravitino, but they are produced by the decay of modular field $T$ and scalar field $Y$. Because the reheating temperature $T_R$ is about order $\sim O(10^{10})$ GeV and the mass of gravitino is $3.16 \times 10^{12}$ GeV, it is not reproduced after the reheating of the universe. The gravitinos are produced almost instantly just after the end of inflation through $Y$ and $T$, not from inflaton. Because the decay time appears very rapid, gravitinos disappear before the BBN stage of the universe. The effects of the lightest supersymmetric particles (LSP) produced by gravitinos may be important to investigate more carefully, if the LSP's are the candidate of dark matter.

hep-ph↗

arXiv2010

Reheating Temperature after Inflation in No-Scale Supergravity

By using a No-Scale Supergravity model, which was proved well to explain WMAP observations appropriately, a mechanism of preheating just after the end of inflation is investigated. By using the canonically normalized and diagonalized scalars, the decay rates of these fields are calculated inflaton $S$ into gauge sector fields. The reheating temperature is estimated by both the stability condition of Boltzmann equation and the instant preheating mechanism. The both of reheating temperatures are almost the same order of magnitude $\sim O(10^{10})$ GeV. Because two mechanisms are completely independent processes, the former is caused through the inflaton decays into gauge fields and gauginons and the latter is caused by the scattering process of two inflatons into two right handed sneutrinos, which will decay into Higgs fields and other minimal SUSY standard model (MSSM) particles, we conclude that both mechanisms play essential roles in the preheating process after inflation.

hep-ph↗

arXiv2010

Gravitino Production after Inflation in No-Scale Supergravity

By using a No-Scale Supergravity model, which was proved to explain WMAP observations appropriately, a mechanism of supersymmetry breaking and a preheating just after the end of inflation are investigated. Non-thermal production rate of gravitino is estimated as well as supersymmetry breaking mechanism numerically. The supersymmetry breaking is triggered by the inflaton superfield alone and the interchange of supersymmetry breaking fields does not occur in our model. By the instant preheating mechanism, the preheating temperature is calculated through the process where the inflaton decays into right handed sneutrinos, which will decay into Higgs fields and others. The obtained value of the yield variable for gravitino is rather large, however, the primordial gravitinos decay very rapidly and the preheating temperature is lower than the gravitino mass, the effect to the standard Big Bang Nucleosynthesis (BBN) scenario is negligible. Though a tachyonic state seems to appear from modular field T, it will be solved by assuming the spontaneous breaking of modular invariance. Whether or not the fact is a defect, we emphasize that the model still seems phenomenologically effective.

hep-ph↗

arXiv2009

(0,2) Gauged Linear Sigma Model on Supermanifold

We construct (0,2), D=2 gauged linear sigma model on a supermanifold in both the Abelian gauge group and the non-Abelian gauge group. The $\hat{U}$ operator provides consistency conditions for satisfying the SUSY invariance. Contrary to the Abelian gauge group, it is not essential to introduce the new operator in order to check the exact SUSY invariance of the Lagrangian density. However, in order to introduce the (0,2) chiral superfields, we need the $\hat{U}$ operator, because we can not define the (0,2) chirality conditions of the (0,2) chiral superfields without introducing the new operator by using $\hat{U}$ and the enlarged operator \hat{U}^{a} was obtained from the conditions that yield the (0,2) supersymmetric invariance of the Lagrangian density of the (0,2) U(N) gauged linear sigma model in superfield formalism. We found that the consistency conditions for the Abelian gauge group which assure the (0,2) supersymmetric invariance of Lagrangian density agree with (0,2) chirality conditions for superpotential. The supermanifold \mathcal{M}^{m|n} becomes the super weighted complex projective space WCP^{m-1|n} in U(1) case, which is considered as an example of Calabi-Yau supermanifold.

hep-th↗

arXiv2006

Angular Power Spectrum in Modular Invariant Inflation Model

We propose a scalar potential of inflation, motivated by modular invariant supergravity, and compute the angular power spectra of the adiabatic density perturbations that result from this model. The potential consists of three scalar fields, S, Y and T, together with two free parameters. By fitting the parameters to cosmological data at the fixed point T=1, we find that the potential behaves like the single-field potential of S, which slowly rolls down along the minimized trajectory in Y. We further show that the inflation predictions corresponding to this potential provide a good fit to the recent three-year WMAP data, e.g. the spectral index n_s = 0.951. The TT and TE angular power spectra obtained from our model almost completely coincide with the corresponding results obtained from the \LambdaCDM model. We conclude that our model is considered to be an adequate theory of inflation that explains the present data, although the theoretical basis of this model should be further explicated.

astro-ph↗

arXiv2006

Angular Power Spectrum and Dilatonic Inflation in Modular-Invariant Supergravity

The angular power spectrum is investigated in the model of supergravity, incorporating the target-space duality and the non-perturbative gaugino condensation in the hidden sector. The inflation and supersymmetry breaking occur at once by the interplay between the dilaton field as inflaton and the condensate gauge-singlet field. The model satisfies the slow-roll condition which solves the η-problem. When the particle rolls down along the minimized trajectory of the potential at a duality invariant fixed point T=1, we can obtain the e-fold value \sim 57. And then the cosmological parameters obtained from our model well match with the recent WMAP data combined with other experiments. The TT and TE angular power spectra also show that our model is compatible with the data for l > 20. However, the best fit value of τin our model is smaller than that of the ΛCDM model. These results suggest that, among supergravity models of inflation, the modular-invariant supergravity seems to open a hope to construct the realistic theory of particles and cosmology.

hep-ph↗

arXiv2004

Dilatonic Inflation and SUSY Breaking in Modular-Invariant Supergravity

The theory of inflation will be investigated as well as supersymmetry breaking in the context of supergravity, incorporating the target-space duality and the non-perturbative gaugino condensation in the hidden sector. The inflation and supersymmetry breaking occur at once by the interplay between the dilaton field as inflaton and the condensate gauge-singlet field. The model satisfies the slow-roll condition which solves the eta-problem. When the particle rolls down along the minimized trajectry of the potential V(S,Y) at a duality invariant fixed point T=1, we can obtain the e-fold value \sim 57. And then the cosmological parameters obtained from our model well match with the recent WMAP data combined with other experiments. This observation is suggesting to consider the string-inspired supergravity as the fundamental of the theory of the evolution of the universe as well as the particle theory.

hep-ph↗

arXiv2004

General Relativity with Torsion

General Relativity with nonvanishing torsion has been investigated in the first order formalism of Poincare gauge field theory. In the presence of torsion, either side of the Einstein equation has the nonvanishing covariant divergence. This fact turned out to be self-consistent in the framework under consideration. By using Noether's procedure with the definition of the Lie derivative where the general coordinate transformation and the local Lorentz rotation are combined, the revised covariant divergence of the energy momentum is consistently obtained. Subsequently we have definitely derived the spin correction to the energy momentum tensor for the Dirac field and the Rarita-Schwinger field in the Einstein equation. We conjecture that the accelerated expansion of the universe possibly arises due to the spin correction in our framework.

gr-qc↗

arXiv2003

Dilatonic Inflation and SUSY Breaking in String-inspired Supergravity

The theory of inflation will be investigated as well as supersymmetry breaking in the context of supergravity, incorporating the target-space duality and the nonperturbative gaugino condensation in the hidden sector. We found an inflationary trajectory of a dilaton field and a condensate field which breaks supersymmetry at once. The model satisfies the slow-roll condition which solves the eta-problem. When the particle rolls down along the minimized trajectory of the potential V(S,Y) at a duality invariant point of T=1, we can obtain the e-fold value \sim 57. And then the cosmological parameters obtained from our model well match the recent WMAP data combined with other experiments. This observation suggests one to consider the string-inspired supergravity as a fundamental theory of the evolution of the universe as well as the particle theory.

hep-ph↗

arXiv2001

Spin-3/2 Fermions in Twistor Formalism

Consistency conditions for the local existence of massless spin 3/2 fields has been explored that the field equations for massless helicity 3/2 are consistent iff the space-time is Ricci-flat and that in Minkowski space-time the space of conserved charges for the fields is its twistor space itself. After considering the twistorial methods to study such massless helicity 3/2 fields, we derive in flat space-time that the charges of spin-3/2 fields defined topologically by the first Chern number of their spin-lowered self-dual Maxwell fields, are given by their twistor space, and in curved space-time that the (anti-)self-duality of the space-time is the necessary condition. Since in N=1 supergravity torsions are the essential ingredients, we generalize our space-time to that with torsion (Einstein-Cartan theory) and have investigated the consistency of existence of spin 3/2 fields in it. A simple solution is found that the space-time has to be conformally (anti-)self-dual, left-(or right-)torsion-free. The integrability condition on $α$-surface shows that the (anti-)self-dual Weyl spinor can be described only by the covariant derivative of the right-(left-)handed-torsion.

hep-th↗