Gamma-ray Constraints on Hadronic and Leptonic Activities of Decaying Dark Matter (2009)
Chen, Chuan-Ren, Mandal, Sourav K., Takahashi, Fuminobu
While the excess in cosmic-ray electrons and positrons reported by PAMELA and Fermi may be explained by dark matter decaying primarily into charged leptons, this does not necessarily mean that dark...
Non-thermal Gravitino Dark Matter in Gauge Mediation (2009)
Hamaguchi, Koichi, Kitano, Ryuichiro, Takahashi, Fuminobu
We show that gravitinos produced by decays of a supersymmetry breaking scalar field (the pseudo-moduli field) can naturally explain the observed abundance of dark matter in a certain class of the...
The R-axion and non-Gaussianity (2009)
Nakayama, Kazunori, Takahashi, Fuminobu
We study cosmological implications of an R-axion, a pseudo Nambu-Goldstone boson associated with spontaneous breaking of an U(1)_R symmetry, focusing on its quantum fluctuations generated during...
Cosmic-ray Electron and Positron Excesses from Hidden Gaugino Dark Matter (2009)
Shirai, Satoshi, Takahashi, Fuminobu, Yanagida, T. T.
We study a scenario that a hidden gaugino dark matter decays into the standard-model particles (and their supersymmetric partners) through a kinetic mixing with the gaugino of a U(1)B-L broken at a...
Conformal Supersymmetry Breaking in Vector-like Gauge Theories (2009)
Takahashi, Fuminobu, Yanagida, T. T., Yonekura, Kazuya
A new class of models of dynamical supersymmetry breaking is proposed. The models are based on SU(N_C) gauge theories with N_F(
Non-Gaussianity from Isocurvature Perturbations : Analysis of Trispectrum (2009)
Kawakami, Etsuko, Kawasaki, Masahiro, Nakayama, Kazunori, Takahashi, Fuminobu
Non-Gaussianity may exist in the CDM isocurvature perturbation. We provide general expressions for the bispectrum and trispectrum of both adiabatic and isocurvature pertubations. We apply our result...
Ando, Masaki, Kawamura, Seiji, Sato, Shuichi, Nakamura, Takashi, Tsubono, Kimio, Araya, Akito, ...
DECIGO pathfinder (DPF) is a milestone satellite mission for DECIGO (DECi-hertz Interferometer Gravitational wave Observatory), which is a future space gravitational wave antenna. DECIGO is expected...
Shirai, Satoshi, Takahashi, Fuminobu, Yanagida, T. T.
We show that R-parity violating decay of Wino dark matter of mass \sim 3 TeV can naturally account for the flux and spectral shape of the cosmic-ray electrons and positrons observed by the PAMELA and...
Phenomenological Aspects of Horava-Lifshitz Cosmology (2009)
Mukohyama, Shinji, Nakayama, Kazunori, Takahashi, Fuminobu, Yokoyama, Shuichiro
We show that, assuming the dispersion relation proposed recently by Horava in the context of quantum gravity, radiation energy density exhibits a peculiar dependence on the scale factor; the...
Decaying Hidden Gaugino as a Source of PAMELA/ATIC Anomalies (2009)
Shirai, Satoshi, Takahashi, Fuminobu, Yanagida, T. T.
We study a scenario that a U(1) hidden gaugino constitutes the dark matter in the Universe and decays into a lepton and slepton pair through a mixing with a U(1)B-L gaugino. We find that the...
Runaway Dynamics and Supersymmetry Breaking (2009)
Takahashi, Fuminobu, Yanagida, T. T., Yonekura, Kazuya
Supersymmetric SU(N_C) gauge theories possess runaway-type superpotentials for N_F < N_C, where N_F is the flavor number of massless quarks. We show that the runaway behavior can be stabilized for...
Decaying gravitino dark matter and an upper bound on the gluino mass (2009)
Hamaguchi, Koichi, Takahashi, Fuminobu, Yanagida, T. T.
We show that, if decaying gravitino dark matter is responsible for the PAMELA and ATIC/PPB-BETS anomalies in the cosmic-ray electron and positron fluxes, both a reheating temperature and a gluino...
Gravitational Dark Matter Decay and the ATIC/PPB-BETS Excess (2009)
Takahashi, Fuminobu, Komatsu, Eiichiro
The hidden scalar field, which couples to the visible sector only through Planck-suppressed interactions, is a candidate for dark matter owing to its long lifetime. Decay of such a scalar field...
Dark Matter Model Selection and the ATIC/PPB-BETS anomaly (2008)
Chen, Chuan-Ren, Hamaguchi, Koichi, Nojiri, Mihoko M., Takahashi, Fuminobu, Torii, Shoji
We argue that we may be able to sort out dark matter models in which electrons are generated through the annihilation and/or decay of dark matter, by using a fact that the initial energy spectrum is...
Decaying Hidden Gauge Boson and the PAMELA and ATIC/PPB-BETS Anomalies (2008)
Chen, Chuan-Ren, Nojiri, Mihoko M., Takahashi, Fuminobu, Yanagida, T. T.
We show that the PAMELA anomaly in the positron fraction as well as the ATIC/PPB-BETS excesses in the e^- + e^+ flux are simultaneously explained in our scenario that a hidden U(1)H gauge boson...
Cosmological Moduli Problem from Thermal Effects (2008)
Nakayama, Kazunori, Takahashi, Fuminobu
We estimate the cosmological abundance of a modulus field that has dilatonic couplings to gauge fields, paying particular attention to thermal corrections on the modulus potential. We find that a...
High-energy Cosmic-Ray Positrons from Hidden-Gauge-Boson Dark Matter (2008)
Chen, Chuan-Ren, Takahashi, Fuminobu, Yanagida, T. T.
We provide a scenario in which a hidden U(1) gauge boson constitutes dark matter of the Universe and decays into the standard-model particles through a kinetic mixing with an $U(1)_{B-L}$ gauge...
Gravity Mediation of Supersymmetry Breaking with Dynamical Metastability (2008)
Takahashi, Fuminobu, Yanagida, T. T., Yonekura, Kazuya
We argue that the Polonyi problem can be avoided when our supersymmetry-breaking vacuum is surrounded by many supersymmetric vacua. We construct a dynamical class of supersymmetry-breaking models to...
Cosmic rays from Leptonic Dark Matter (2008)
Chen, Chuan-Ren, Takahashi, Fuminobu
If dark matter possesses a lepton number, it is natural to expect the dark-matter annihilation and/or decay mainly produces the standard model leptons, while negligible amount of the antiproton is...
Hilltop Non-Gaussianity (2008)
Kawasaki, Masahiro, Nakayama, Kazunori, Takahashi, Fuminobu
We study non-Gaussianity induced by a pseudo Nambu-Goldstone boson with a cosine-type scalar potential. We focus on how the non-Gaussianity is affected when the pseudo Nambu-Goldstone boson rolls...
A General Analysis of Non-Gaussianity from Isocurvature Perturbations (2008)
Kawasaki, Masahiro, Nakayama, Kazunori, Sekiguchi, Toyokazu, Suyama, Teruaki, Takahashi, Fuminobu
Light scalars may be ubiquitous in nature, and their quantum fluctuations can produce large non-Gaussianity in the cosmic microwave background temperature anisotropy. The non-Gaussianity may be...
Non-Gaussianity from Baryon Asymmetry (2008)
Kawasaki, Masahiro, Nakayama, Kazunori, Takahashi, Fuminobu
We study a scenario that large non-Gaussianity arises from the baryon asymmetry of the Universe. There are baryogenesis scenarios containing a light scalar field, which may result in baryonic...
Gamma rays and positrons from a decaying hidden gauge boson (2008)
Chen, Chuan-Ren, Takahashi, Fuminobu, Yanagida, T. T.
We study a scenario that a hidden gauge boson constitutes the dominant component of dark matter and decays into the standard model particles through a gauge kinetic mixing. Interestingly, gamma rays...
Gauge Mediation with Sequestered Supersymmetry Breaking (2008)
Shirai, Satoshi, Takahashi, Fuminobu, Yanagida, T. T., Yonekura, Kazuya
Gauge mediation models have two drawbacks, that is, the so-called \mu-problem and a lack of predictability of the gravitino dark matter abundance. We show that conformal sequestering in the...
Non-Gaussianity from isocurvature perturbations (2008)
Kawasaki, Masahiro, Nakayama, Kazunori, Sekiguchi, Toyokazu, Suyama, Teruaki, Takahashi, Fuminobu
We develop a formalism to study non-Gaussianity in both curvature and isocurvature perturbations. It is shown that non-Gaussianity in the isocurvature perturbation between dark matter and photons...
Isocurvature fluctuations in Affleck-Dine mechanism and constraints on inflation models (2008)
Kasuya, Shinta, Kawasaki, Masahiro, Takahashi, Fuminobu
We reconsider the Affleck-Dine mechanism for baryogenesis and show that the baryonic isocurvature fluctuations are generated in many inflation models in supergravity. The inflationary scale and the...
The Anthropic Solution to the Strong CP problem and its Cosmological Implications (2008)
We point out that the long-standing strong CP problem can be resolved by the anthropic principle. The key ideas are:(i) to allow explicit breaking(s) of the Peccei-Quinn symmetry which reduces the...
Non-Gaussianity from Symmetry (2008)
Suyama, Teruaki, Takahashi, Fuminobu
We point out that a light scalar field fluctuating around a symmetry-enhaced point can generate large non-Gaussianity in density fluctuations. We name such a particle as an "ungaussiton", a scalar...
Gravitational Waves as a Probe of the Gravitino Mass (2008)
Takahashi, Fuminobu, Yanagida, T. T., Yonekura, Kazuya
If gaugino condensations occur in the early universe, domain walls are produced as a result of the spontaneous breaking of a discrete R symmetry. Those domain walls eventually annihilate with one...
A Problem of the QCD Axion in Supergravity (2007)
Endo, Motoi, Takahashi, Fuminobu, Yanagida, T. T.
This paper has been withdrawn by the authors due to a crucial error in equation 12.
Dark Matter in Gauge Mediated Supersymmetry Breaking using Metastable Vacua (2007)
Endo, Motoi, Takahashi, Fuminobu
We point out that, in a class of gauge mediation models using metastable supersymmetry breaking vacua, the minimum of the supersymmetry breaking field in the early universe is dynamically deviated...
Entropy production by Q-ball decay for diluting long-lived charged particles (2007)
Kasuya, Shinta, Takahashi, Fuminobu
The cosmic abundance of a long-lived charged particle such as a stau is tightly constrained by the catalyzed big bang nucleosynthesis. One of the ways to evade the constraints is to dilute those...
Inflaton Decay in Supergravity and Gravitino Problem (2007)
We have recently shown that, if the inflaton has a nonzero vacuum expectation value, it generically couples to any matter fields that appear in the superpotential at the tree level, and to any gauge...
Inflaton Decay in Supergravity (2007)
Endo, Motoi, Takahashi, Fuminobu, Yanagida, T. T.
We discuss inflaton decay in supergravity, taking account of the gravitational effects. It is shown that, if the inflaton has a nonzero vacuum expectation value, it generically couples to any matter...
Gravitino Dark Matter from Inflaton Decay (2007)
We discuss a scenario that gravitinos produced non-thermally by an inflaton decay constitute dark matter in the present universe. We find that this scenario is realized for wide ranges of the...
Increasing the effective number of neutrinos with decaying particles (2007)
Ichikawa, Kazuhide, Kawasaki, Masahiro, Nakayama, Kazunori, Senami, Masato, Takahashi, Fuminobu
We present models of decaying particles for increasing the effective number of neutrinos N_nu after big bang nucleosynthesis but before the structure formation begins. We point out that our scenario...
Retrofitted Gravity Mediation without the Gravitino-overproduction Problem (2007)
Endo, Motoi, Takahashi, Fuminobu, Yanagida, T. T.
We propose a retrofitted gravity mediation model which alleviates the gravitino overproduction from decays of an inflaton and a supersymmetry breaking field. In the model, we introduce an approximate...
Anomaly-Induced Inflaton Decay and Gravitino-Overproduction Problem (2007)
Endo, Motoi, Takahashi, Fuminobu, Yanagida, T. T.
We point out that the inflaton spontaneously decays into any gauge bosons and gauginos via the super-Weyl, Kahler and sigma-model anomalies in supergravity, once the inflaton acquires a non-vanishing...
The Decay of the Inflaton in No-scale Supergravity (2006)
Endo, Motoi, Kadota, Kenji, Olive, Keith A., Takahashi, Fuminobu, Yanagida, T. T.
We study the decay of the inflaton in no-scale supergravity and show that decay due to the gravitational interactions through supergravity effects is highly suppressed relative to the case in minimal...
Ichikawa, Kazuhide, Kawasaki, Masahiro, Takahashi, Fuminobu
We derive constraint on the effective number of neutrino species N_nu from the cosmic microwave background power spectrum of the WMAP and galaxy clustering power spectrum of the SDSS luminous red...
The Gravitino-Overproduction Problem in Inflaton Decay (2006)
Kawasaki, Masahiro, Takahashi, Fuminobu, Yanagida, T. T.
We show that the gravitino-overproduction problem is prevalent among inflation models in supergravity. An inflaton field generically acquires (effective) non-vanishing auxiliary field, if the Kahler...
Spontaneous Non-thermal Leptogenesis in High-scale Inflation Models (2006)
Endo, Motoi, Takahashi, Fuminobu, Yanagida, T. T.
We argue that a non-thermal leptogenesis occurs spontaneously, without direct couplings of the inflaton with right-handed neutrinos, in a wide class of high-scale inflation models such as the chaotic...
Inflaton Decay through Supergravity Effects (2006)
Endo, Motoi, Kawasaki, Masahiro, Takahashi, Fuminobu, Yanagida, T. T.
We point out that supergravity effects enable the inflaton to decay into all matter fields, including the visible and the supersymmetry breaking sectors, once the inflaton acquires a non-vanishing...
Non-thermal Production of Dark Matter from Late-Decaying Scalar Field at Intermediate Scale (2006)
Endo, Motoi, Takahashi, Fuminobu
We examine non-thermal dark matter production from a late-decaying scalar field, with a particular attention on non-renormalizable operators of D=5 through which the scalar field decays into the...
We need lab experiments to look for axion-like particles (2006)
Jaeckel, Joerg, Masso, Eduard, Redondo, Javier, Ringwald, Andreas, Takahashi, Fuminobu
The PVLAS signal has renewed the interest in light bosons coupled to the electromagnetic field. However, astrophysical bounds coming from the lifetime of the sun and the CAST experiment are seemingly...
The Gravitino-Overproduction Problem in Inflationary Universe (2006)
Kawasaki, Masahiro, Takahashi, Fuminobu, Yanagida, T. T.
We show that the gravitino-overproduction problem is prevalent among inflation models in supergravity. An inflaton field \phi generically acquires (effective) non-vanishing auxiliary field G_\phi, if...
Moduli/Inflaton Mixing with Supersymmetry Breaking Field (2006)
Endo, Motoi, Hamaguchi, Koichi, Takahashi, Fuminobu
A heavy scalar field such as moduli or an inflaton generally mixes with a field responsible for the supersymmetry breaking. We study the scalar decay into the standard model particles and their...
Gravitino Overproduction in Inflaton Decay (2006)
Kawasaki, Masahiro, Takahashi, Fuminobu, Yanagida, T. T.
Most of the inflation models end up with non-vanishing vacuum expectation values of the inflaton fields \phi in the true vacuum, which induce, in general, nonvanishing auxiliary field G_\phi for the...
Moduli-Induced Gravitino Problem (2006)
Endo, Motoi, Hamaguchi, Koichi, Takahashi, Fuminobu
We investigate the cosmological moduli problem by studying a modulus decay in detail and find that the branching ratio of the gravitino production is generically of O(0.01-1), which causes another...
Unification of Dark Energy and Dark Matter (2005)
Takahashi, Fuminobu, Yanagida, T. T.
We propose a scenario in which dark energy and dark matter are described in a unified manner. The ultralight pseudo-Nambu-Goldstone (pNG) boson, A, naturally explains the observed magnitude of dark...
511 keV line from Q balls in the Galactic Center (2005)
Kasuya, Shinta, Takahashi, Fuminobu
The 511 keV photons from the galactic center can be explained by positrons produced through Q-ball decay. In the scheme of gauge-mediated supersymmetry breaking, large Q balls with lepton charge are...
Ichikawa, Kazuhide, Kawasaki, Masahiro, Takahashi, Fuminobu
We study how the oscillations of the neutrinos affect their thermalization process during the reheating period with temperature O(1) MeV in the early universe. We follow the evolution of the neutrino...
Q-ball Instability due to U(1) Breaking (2005)
Kawasaki, Masahiro, Konya, Kenichiro, Takahashi, Fuminobu
Q-ball is a non-topological soliton whose stability is ensured by global U(1) symmetry. We study a Q-ball which arises in the Affleck-Dine mechanism for baryogenesis and consider its possible...
Smallness of Baryon Asymmetry from Split Supersymmetry (2005)
Kasuya, Shinta, Takahashi, Fuminobu
The smallness of the baryon asymmetry in our universe is one of the greatest mysteries and may originate from some profound physics beyond the standard model. We investigate the Affleck-Dine...
Late-time entropy production due to the decay of domain walls (2004)
Kawasaki, Masahiro, Takahashi, Fuminobu
It is shown that late-time decay of domain walls can dilute unwanted relics such as moduli, if the universe was dominated by frustrated domain walls with tension $\sigma = (1 - 100 TeV)^3$. Since...
Suppressed neutrino oscillations and large lepton asymmetries (2004)
Dolgov, A. D., Takahashi, Fuminobu
It is shown that hypothetical neutrino-majoron coupling can suppress neutrino flavor oscillations in the early universe, in contrast to the usual weak interaction case. This reopens a window for a...
Making waves on CMB power spectrum and inflaton dynamics (2004)
Kawasaki, Masahiro, Takahashi, Fuminobu, Takahashi, Tomo
We discuss cosmic microwave background anisotropies in models with an unconventional primordial power spectrum. In particular, we consider an initial power spectrum with some ``spiky'' corrections....
D-term Instability in Flat Directions and its Cosmological Implication (2004)
Kawasaki, Masahiro, Takahashi, Fuminobu
We study dynamics of flat directions in the minimal supersymmetric standard model taking account of its constituent fields. It is found that there exist new instabilities due to the D-term potential...
Kawasaki, Masahiro, Takahashi, Fuminobu
Flat directions in the minimal supersymmetric standard model are known to deform into non-topological solitons, Q-balls, which generally possess both baryon and lepton asymmetries. We investigate how...
Solving the discrepancy among the light elements abundances and WMAP (2004)
Ichikawa, Kazuhide, Kawasaki, Masahiro, Takahashi, Fuminobu
Within the standard big bang nucleosynthesis (BBN) and cosmic microwave background (CMB) framework, the baryon density measured by the Wilkinson Microwave Anisotropy Probe (WMAP) or the primordial D...
Do neutrino flavor oscillations forbid large lepton asymmetry of the universe ? (2004)
Dolgov, A. D., Takahashi, Fuminobu
It is shown that hypothetical neutrino-majoron coupling can suppress neutrino flavor oscillations in the early universe, in contrast to the usual weak interaction case. This reopens a window for a...
Can MSSM Particle be the Inflaton? (2003)
Kasuya, Shinta, Moroi, Takeo, Takahashi, Fuminobu
We consider the possibility of using one of the $D$-flat directions in the minimal supersymmetric standard model (MSSM) as the inflaton. We show that the flat direction consisting of (first...
Curvatons in Supersymmetric Models (2003)
Hamaguchi, Koichi, Kawasaki, Masahiro, Moroi, Takeo, Takahashi, Fuminobu
We study the curvaton scenario in supersymmetric framework paying particular attention to the fact that scalar fields are inevitably complex in supersymmetric theories. If there are more than one...
Spontaneous baryogenesis in flat directions (2003)
Takahashi, Fuminobu, Yamaguchi, Masahide
We discuss a spontaneous baryogenesis mechanism in flat directions. After identifying the Nambu-Goldstone mode which derivatively couples to the associated $U$(1) current and rotates due to the...
Inflation model with lower multipoles of the CMB suppressed (2003)
Kawasaki, Masahiro, Takahashi, Fuminobu
The recent observation of the cosmic microwave background anisotropy by the WMAP confirmed that the lower multipoles are considerably suppressed. From the standpoint of the cosmic variance, it is...
MSSM curvaton in the gauge-mediated SUSY breaking (2003)
Kasuya, S., Kawasaki, M., Takahashi, Fuminobu
We study the curvaton scenario using the MSSM flat directions in the gauge-mediated SUSY breaking model. We find that the fluctuations in the both radial and phase directions can be responsible for...
Baryogenesis in a flat direction with neither baryon nor lepton charge (2003)
Chiba, Takeshi, Takahashi, Fuminobu, Yamaguchi, Masahide
We present a new mechanism of spontaneous baryogenesis. Usually such mechanisms require a derivative coupling between a scalar field and baryon current. In our model, the scalar field instead...
Affleck-Dine mechanism with negative thermal logarithmic potential (2003)
Kasuya, S., Kawasaki, M., Takahashi, Fuminobu
We investigate whether the Affleck-Dine (AD) mechanism works when the contribution of the two-loop thermal correction to the potential is negative in the gauge-mediated supersymmetry breaking models....
Kasuya, S., Kawasaki, M., Takahashi, Fuminobu
We find that there exists a soliton-like solution ``I-ball'' in theories of a real scalar field if the scalar potential satisfies appropriate conditions. Although the I-ball does not have any...
Large lepton asymmetry from Q-balls (2002)
Kawasaki, M., Takahashi, Fuminobu, Yamaguchi, Masahide
We propose a scenario which can explain large lepton asymmetry and small baryon asymmetry simultaneously. Large lepton asymmetry is generated through Affleck-Dine (AD) mechanism and almost all the...
On the Moduli Problem and Baryogenesis in Gauge-mediated SUSY Breaking Models (2001)
Kasuya, S., Kawasaki, M., Takahashi, Fuminobu
We investigate whether the Affleck-Dine mechanism can produce sufficient baryon number of the universe in the gauge-mediated SUSY breaking models, while evading the cosmological moduli problem by...
Adiabatic and isocurvature fluctuations of Affleck-Dine field in D-term inflation model (2001)
Kawasaki, Masahiro, Takahashi, Fuminobu
We reconsider fluctuations of Affleck-Dine (AD) field in a D-term inflation model. Contrary to the previous analysis, we find that the spectrum of the adiabatic fluctuations is almost scale invariant...