Homotopy operators and identity-based solutions in cubic superstring field theory
We construct a class of nilpotent operators using the BRST current and ghost fields in superstring theory. The operator can be realized in cubic superstring field theory as a kinetic operator in the background of an identity-based solution. For a particular type of the deformed BRST operators, we find a homotopy operator and discuss its relationship to the cohomology in a similar way to the bosonic case, which has been elaborated by the authors.

title: Tachyon condensation and universal solutions in string field theory
abstract: We investigate a non-perturbative vacuum in open string field theory expanded around the analytic classical solution which has been found in the universal Fock space generated by matter Virasoro generators and ghost oscillators. We carry out level-truncation analyses up to level (6,18) in the theory around one-parameter families of the solution. We observe that the value of the vacuum energy cancels the D-brane tension as the approximation level is increased, but this non-perturbative vacuum disappears at the boundary of the parameter space. These results provide strong evidence for the conjecture that, although the universal solutions are pure gauge in almost all the parameter space, they are regarded as the tachyon vacuum solution at the boundary.

title: On the Generalized Gluing and Resmoothing Theorem
abstract: The generalized gluing and resmoothing theorem originally proved by LeClair, Peskin and Preitschopf, gives a powerful formula for the fused vertex obtained by contracting any two vertices in string field theories. Although the theorem is naturally expected to hold for the vertices at any loop level, the original proof was restricted to the vertices at tree level. Here we present a simplified proof for the tree level theorem and then prove explicitly the extended version at one-loop level. We also find that a non-trivial sign factor, which depends on the string states to be contracted, appears in the theorem. This sign factor turns out to be essential for reproducing correctly the conformal field theory correlation function on the torus.

title: Marginal deformations and closed string couplings in open string field theory
abstract: We investigate analytic classical solutions in open string field theory which are constructed in terms of marginal operators. In the classical background, we evaluate a coupling between an on-shell closed string state and the open string field. The resulting coupling exhibits periodic behavior as expected from the marginal boundary deformation of background Wilson lines or a marginal tachyon lump. We confirm that the solutions in open string field theory correspond to a class of marginal deformations in conformal field theory.

title: Level truncation analysis of exact solutions in open string field theory
abstract: We evaluate vacuum energy density of Schnabl's solution using the level truncation calculation and the total action including interaction terms. The level truncated solution provides vacuum energy density expected both for tachyon vacuum and trivial pure gauge. We discuss the role of the phantom term to reproduce correct vacuum energy.

title: Closed string amplitudes in open string field theory
abstract: We investigate gauge invariant operators corresponding to on-shell closed string states in open string field theory. Using both oscillator representation and conformal mapping techniques, we calculate a two closed string tachyon amplitude that connects two gauge invariant operators by an open string propagator. We find that this amplitude is in a complete agreement with the usual disc amplitude.

title: Candidates for the inflaton in quiver gauge theory
abstract: The inflaton necessary to implement the mechanism of inflationary cosmology has natural candidates in quiver gauge theory. We discuss the dimensionless coefficients of quartic couplings and enumerate scalars which are singlet under the low-energy gauge group. The inflaton mass is generally predicted to be in the TeV region, close to 4 TeV for one specific unified model. A quartic inflaton potential, and a mutated hybrid inflation, are discussed. They can give adequate inflation and appropriate fluctuations but different spectral indices.

title: The ASTRO-H X-ray Observatory
abstract: The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the highenergy universe via a suite of four instruments, covering a very wide energy range, from 0.3 keV to 600 keV. These instruments include a high-resolution, high-throughput spectrometer sensitive over 0.3–12 keV with high spectral resolution of ΔE ≦ 7 eV, enabled by a micro-calorimeter array located in the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers covering 5–80 keV, located in the focal plane of multilayer-coated, focusing hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4–12 keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the 40–600 keV band. The simultaneous broad bandpass, coupled with high spectral resolution, will enable the pursuit of a wide variety of important science themes.

title: Implications of dark energy parametrizations for the determination of the curvature of the universe
abstract: We investigate how the nature of dark energy affects the determination of the curvature of the universe, using recent observations. For this purpose, we consider the constraints on the matter and dark energy density using observations of type Ia supernovae, the baryon acoustic oscillation peak and the cosmic microwave background with dark energy equations of state of several types. Although it is usually said that the combination of current observations favours a flat universe, we found that a relatively large parameter space allows the universe to be open for a particular model of dark energy. We also discuss what kind of dark energy model or prior allows a non-flat universe.

title: Strongly scale-dependent polyspectra from curvaton self-interactions
abstract: We study the scale dependence of the non-linearity parameters fNL and gNL in curvaton models with self-interactions. We show that the spectral indices nfNL = d ln|fNL|/d ln k and ngNL = d ln|gNL|/d ln k can take values much greater than the slow-roll parameters and the spectral index of the power spectrum. This means that the scale-dependence of the bi and trispectrum could be easily observable in this scenario with Planck, which would lead to tight additional constraints on the model. Inspite of the highly non-trivial behaviour of fNL and gNL in the curvaton models with self-interactions, we find that the model can be falsified if gNL(k) is also observed.

title: Cosmic degeneracy with dark energy equation of state
abstract: We discuss a degeneracy between the geometry of the universe and the dark energy equation of state wX which exists in the power spectrum of the cosmic microwave background. In particular, for the case with wX<−1, this degeneracy has interesting implications to a lower bound on wX from observations. It is also discussed how this degeneracy can be removed using current observations of type Ia supernovae.