Phase ambiguity of the threshold amplitude in pp -> pp\pi^0

Measurements of spin observables in pp -> {\vec p}{\vec p}\pi^0 are suggested to remove the phase ambiguity of the threshold amplitude. The suggested measurements complement the IUCF data on {\vec p}{\vec p} -> pp\pi^0 to completely determine all the twelve partial wave amplitudes, taken into consideration by Mayer et.al. [15] and Deepak, Haidenbauer and Hanhart [20].Comment: 4 pages, 1 table

Nebular Spectra and Explosion Asymmetry of Type Ia Supernovae

The spectral signatures of asymmetry in Type Ia Supernova (SN Ia) explosions are investigated, using a sample of late-time nebular spectra. First, a kinematical model is constructed for SN Ia 2003hv, which can account for the main features in its optical, Near-Infrared (NIR), and Mid-Infrared (Mid-IR) late-time spectra. It is found that an asymmetric off-center model can explain the observed characteristics of SN 2003hv. This model includes a relatively high density, Fe-rich region which displays a large velocity off-set, and a relatively low density, extended 56Ni-rich region which is more spherically distributed. The high density region consists of the inner stable Fe-Ni region and outer 56Ni-rich region. Such a distribution may be the result of a delayed-detonation explosion, in which the first deflagration produces the global asymmetry in the innermost ejecta, while the subsequent detonation can lead to the bulk spherical symmetry. This configuration, if viewed from the direction of the off-set, can consistently explain the blueshift in some of the emission lines and virtually no observed shift in other lines in SN 2003hv. For this model, we then explore the effects of different viewing angles and the implications for SNe Ia in general. The model predicts that a variation of the central wavelength, depending on the viewing angle, should be seen in some lines (e.g., [Ni II]7378), while the strongest lines (e.g., [Fe III] blend at 4700A) will not show this effect. By examining optical nebular spectra of 12 SNe Ia, we have found that such a variation indeed exists. We suggest that the global asymmetry in the innermost ejecta, as likely imprint of the deflagration flame propagation, is a generic feature of SNe Ia (abridged).Comment: 14 pages, 11 figures, 4 tables. Accepted for publication in the Astrophysical Journal. Minor correction

Inflation from Superstring/M-Theory Compactification with Higher Order Corrections II -- Case of Quartic Weyl Terms --

We present a detailed study of inflationary solutions in M-theory with higher order quantum corrections. We first exhaust all exact and asymptotic solutions of exponential and power-law expansions in this theory with quartic curvature corrections, and then perform a linear perturbation analysis around fixed points for the exact solutions in order to see which solutions are more generic and give interesting cosmological models. We find an interesting solution in which the external space expands exponentially and the internal space is static both in the original and Einstein frames. This may be regarded as moduli stabilization by higher order corrections. Furthermore, we perform a numerical calculation around this solution and find numerical solutions which give enough e-foldings. We also briefly summarize similar solutions in type II superstrings.Comment: 40 pages, 11 figures, v2: additional explanations, refs. added, to appear in PR

Meissner effect in the layered Kane-Mele model with Hubbard interaction

We investigate the magnetic response in the quantum spin Hall phase of the layered Kane-Mele model with Hubbard interaction, and argue a condition to obtain the Meissner effect. The effect of Rashba spin orbit coupling is also discussed.Comment: 4 pages, accepted for publication in Journal of Physics: Conference Series as proceedings of International Symposium "Nanoscience and Quantum Physics 2011" (nanoPHYS'11) held in Toky

Radiation from an accelerated quark via AdS/CFT

In this paper we investigate radiation by an accelerated quark in a strongly coupled gauge theory via AdS/CFT correspondence. According to AdS/CFT dictionary, we can read off energy density or energy flux of the radiation from asymptotic gravitational field in AdS bulk sourced by an accelerated string trailing behind the quark. In the case of an oscillating quark with frequency $\Omega$, we show that the time averaged energy density is asymptotically isotropic and it falls off as $(g_{\text{YM}}^2 N)^{1/2} \Omega^4/R^{2}$ with distance $R$ from the source. In a toy model of a scattered quark by an external field, we simply estimate Poynting vector by the bremsstrahlung radiation and show that the energy flux is anisotropic outgoing radiation. Based on these investigations, we discuss the properties of strongly coupled gauge theory radiation in comparison with electromagnetic radiation.Comment: 16 pages, no figures, accepted for publication in Phys. Rev.

A study of gamma ray bursts with afterglow plateau phases associated with supernovae

The analysis of 176 gamma ray burst (GRB) afterglow plateaus observed by Swift from GRBs with known redshifts revealed that the subsample of long GRBs associated with supernovae (LONG-SNe) - 19 events - presents a very high correlation coefficient between the luminosity at the end of the plateau phase La and the end time of the plateau T*a, hereafter Dainotti relation. Furthermore, these SNe Ib/c associated with GRBs also obey the peak-magnitude stretch relation, similar to that used to standardize the SNe Ia. We here investigate a category of GRBs with plateau and associated with SNe to compare the Dainotti correlation for this sample with the correlation for long GRBs for which no associated SN has been observed (hereafter LONG-NO-SNe, 128 GRBs) and to check whether there is a difference among these sub-samples. We first adopted a non-parametric statistical method to take redshift evolution into account and to check if and how this effect may steepen the slope for the LONG-NO-SNe sample. Therefore, removing selection bias is the first step before any comparison among samples observed at different redshifts could be properly performed. Then, we applied the T-student test to evaluate a statistical difference between the slopes of the two samples. We demonstrate that there is no evolution for the slope of the LONG-NO-SNe sample and no evolution is expected for the LONG-SNe sample at small redshifts. The difference between the slope of the LONG-NO-SNe and the slope of LONG-SNe with firm spectral detection of SN components, is statistically significant. This possibly suggests that, unlike LONG-NO-SNe, LONG-SNe with firm spectroscopic features of the associated SNe might not require a standard energy reservoir in the plateau phase. Therefore, this analysis may open new perspectives in future theoretical investigations of the GRBs with plateau emission and that are associated with SNe.Comment: 11 pages, 10 figures, 2 Tables, in press on Astronomy and Astrophysics, 8 dicember 201

Creation of the universe with a stealth scalar field

The stealth scalar field is a non-trivial configuration without any back-reaction to geometry, which is characteristic for non-minimally coupled scalar fields. Studying the creation probability of the de Sitter universe with a stealth scalar field by the Hartle and Hawking's semi-classical method, we show that the effect of the stealth field can be significant. For the class of scalar fields we consider, creation with a stealth field is possible for a discrete value of the coupling constant and its creation probability is always less than that with a trivial scalar field. However, those creation rates can be almost the same depending on the parameters of the theory.Comment: 7 pages; v2, references added; v3, creation of the open universe adde

The Progenitor of the Type IIb SN 2008ax Revisited

Hubble Space Telescope observations of the site of the supernova (SN) 2008ax obtained in 2011 and 2013 reveal that the possible progenitor object detected in pre-explosion images was in fact multiple. Four point sources are resolved in the new, higher-resolution images. We identify one of the sources with the fading SN. The other three objects are consistent with single supergiant stars. We conclude that their light contaminated the previously identified progenitor candidate. After subtraction of these stars, the progenitor appears to be significantly fainter and bluer than previously measured. Post-explosion photometry at the SN location indicates that the progenitor object has disappeared. If single, the progenitor is compatible with a supergiant star of B to mid-A spectral type, while a Wolf-Rayet (WR) star would be too luminous in the ultraviolet to account for the observations. Moreover, our hydrodynamical modelling shows the pre-explosion mass was $4-5$ $M_\odot$ and the radius was $30-50$ $R_\odot$, which is incompatible with a WR progenitor. We present a possible interacting binary progenitor computed with our evolutionary models that reproduces all the observational evidence. A companion star as luminous as an O9-B0 main-sequence star may have remained after the explosion.Comment: ApJ accepted, 14 pages, 7 figure

Principles of Discrete Time Mechanics: IV. The Dirac Equation, Particles and Oscillons

We apply the principles of discrete time mechanics discussed in earlier papers to the first and second quantised Dirac equation. We use the Schwinger action principle to find the anticommutation relations of the Dirac field and of the particle creation operators in the theory. We find new solutions to the discrete time Dirac equation, referred to as oscillons on account of their extraordinary behaviour. Their principal characteristic is that they oscillate with a period twice that of the fundamental time interval T of our theory. Although these solutions can be associated with definite charge, linear momentum and spin, such objects should not be observable as particles in the continuous time limit. We find that for non-zero T they correspond to states with negative squared norm in Hilbert space. However they are an integral part of the discrete time Dirac field and should play a role in particle interactions analogous to the role of longitudinal photons in conventional quantum electrodynamics.Comment: 27 pages LateX; published versio