Stability of the Accretion Flows with Stalled Shocks in Core-Collapse Supernovae

Bearing in mind the application to the theory of core-collapse supernovae, we performed a global linear analysis on the stability of spherically symmetric accretion flows through a standing shock wave onto a proto neutron star. As unperturbed flows, we adopted the spherically symmetric steady solutions to the Euler equations obtained with realistic equation of state and formulae for neutrino reaction rates taken into account. Then we solved the equations for linear perturbations numerically, and obtained the eigen frequencies and eigen functions. We found (1) the flows are stable for all modes if the neutrino luminosity is lower than $\sim 1\times 10^{52}$ ergs/s for $\dot{M}=1.0M_{\odot}/{\rm s}$. (2) For larger luminosities, the non-radial instabilities are induced, probably via the advection-acoustic cycles. Interestingly, the modes with $\ell=2$ and 3 become unstable at first for relatively low neutrino luminosities, e.g. $\gtrsim 2-3\times 10^{52}$ ergs/s for the same accretion rate, whereas the $\ell=1$ mode is the most unstable for higher luminosities, $\sim 3-7\times 10^{52}$ ergs/s. These are all oscillatory modes. (3) For still larger luminosities, $\sim 7\times 10^{52}$ ergs/s for $\dot{M}=1.0M_{\odot}/{\rm s}$, non-oscillatory modes, both radial and non-radial, become unstable. These non-radial modes were identified as convection. We confirmed the results obtained by numerical simulations that the instabilities induced by the advection-acoustic cycles are more important than the convection for lower neutrino luminosities.Comment: 46 pages, 19 figures, Accepted by Ap

Near-threshold ω\omega-meson production in proton-proton collisions: With or without resonance excitations ?

We present results for the $p p \to p p \omega$ reaction studied by considering two different scenarios: with and without the inclusion of nucleon resonance excitations. The recently measured angular distribution by the COSY-TOF Collaboration at an excess energy of $Q = 173$ MeV and the energy dependence of the total cross section data for $\pi^- p \to \omega n$ are used to calibrate the model parameters. The inclusion of nucleon resonances improves the theoretical prediction for the energy dependence of the total cross section in $pp \to pp\omega$ at excess energies $Q < 31$ MeV. However, it still underestimates the data by about a factor of two, and remains a problem in understanding the reaction mechanism.Comment: Fig.5 and text modified, Latex, 4 pages, 8 embedded figures, uses espcrc1.sty (included), talk presented at PANIC02, Osaka, Japan, 30 September - 4 October 200

Low-scale Supersymmetry from Inflation

We investigate an inflation model with the inflaton being identified with a Higgs boson responsible for the breaking of U(1)B-L symmetry. We show that supersymmetry must remain a good symmetry at scales one order of magnitude below the inflation scale, in order for the inflation model to solve the horizon and flatness problems, as well as to account for the observed density perturbation. The upper bound on the soft supersymmetry breaking mass lies between 1TeV and 10^3TeV. Interestingly, our finding opens up a possibility that universes with the low-scale supersymmetry are realized by the inflationary selection. Our inflation model has rich implications; non-thermal leptogenesis naturally works, and the gravitino and moduli problems as well as the moduli destabilization problem can be solved or ameliorated; the standard-model higgs boson receives a sizable radiative correction if the supersymmertry breaking takes a value on the high side ~10^3TeV.Comment: 23pages, 3 figures. v2: references adde

Interacting Dipoles in Type-I Clathrates: Why Glass-like though Crystal?

Almost identical thermal properties of type-I clathrate compounds to those of glasses follow naturally from the consideration that off-centered guest ions possess electric dipole moments. Local fields from neighbor dipoles create many potential minima in the configuration space. A theoretical analysis based on two-level tunneling states demonstrates that interacting dipoles are a key to quantitatively explain the glass-like behaviors of low-temperature thermal properties of type-I clathrate compounds with off-centered guest ions.From this analysis, we predict the existence of a glass transition

General Analysis of Inflation in the Jordan frame Supergravity

We study various inflation models in the Jordan frame supergravity with a logarithmic Kahler potential. We find that, in a class of inflation models containing an additional singlet in the superpotential, three types of inflation can be realized: the Higgs-type inflation, power-law inflation, and chaotic inflation with/without a running kinetic term. The former two are possible if the holomorphic function dominates over the non-holomorphic one in the frame function, while the chaotic inflation occurs when both are comparable. Interestingly, the fractional-power potential can be realized by the running kinetic term. We also discuss the implication for the Higgs inflation in supergravity.Comment: 16 pages, 1 figur