Numerical solutions of open string field theory in marginally deformed backgrounds
We investigate numerical solutions of bosonic open string field theory in some marginally deformed backgrounds, which are obtained by expanding the action around an identity-based marginal solution with one parameter. We construct numerical solutions in the Siegel gauge and the Landau gauge corresponding to the tachyon vacuum. Their vacuum energy approximately cancels the D-brane tension for larger intervals of the parameter with increasing truncation level. The result is consistent with the previous expectation that the identity-based marginal solution has vanishing energy regardless of the values of the parameter. We also study the marginal branch (M-branch) and the vacuum branch (V-branch) and evaluate not only the vacuum energy but also the gauge invariant overlaps with the graviton and the closed tachyon. We observe that there is a finite bound for the value of the massless field of numerical solutions even in the marginally deformed background.

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: 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: Marginal and Scalar Solutions in Cubic Open String Field Theory
abstract: We find marginal and scalar solutions in cubic open string field theory by using left-right splitting properties of a delta function. The marginal solution represents a marginal deformation generated by a U(1) current, and it is a generalized solution of the Wilson lines one given by the present authors. The scalar solution has a well-defined universal Fock space expression, and it is expressed as a singular gauge transform of the trivial vacuum. The expanded theory around it is unable to be connected with the original theory by the string field redefinition.

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: 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: 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: Adiabatic fluctuations from cosmic strings in a contracting universe
abstract: We show that adiabatic, super-Hubble, and almost scale invariant density fluctuations are produced by cosmic strings in a contracting universe. An essential point is that isocurvature perturbations produced by topological defects such as cosmic strings on super-Hubble scales lead to a source term which seeds the growth of curvature fluctuations on these scales. Once the symmetry has been restored at high temperatures, the isocurvature seeds disappear, and the fluctuations evolve as adiabatic ones in the expanding phase. Thus, cosmic strings may be resurrected as a mechanism for generating the primordial density fluctuations observed today.

title: Cosmological Avatars of the Landscape II: CMB and LSS Signatures
abstract: This is the second paper in the series that confronts predictions of a model of the landscape with cosmological observations. We show here how the modifications of the Friedmann equation due to the decohering effects of long wavelength modes on the wave function of the Universe defined on the landscape leave unique signatures on the CMB spectra and large scale structure (LSS). We show that the effect of the string corrections is to suppress {sigma}{sub 8} and the CMB temperature-temperature (TT) spectrum at large angles, thereby bringing WMAP and SDSS data for {sigma}{sub 8} into agreement. We find interesting features imprinted on the matter power spectrum P(k): power is suppressed at large scales indicating the possibility of primordial voids competing with the integrated Sachs-Wolfe effect. Furthermore, power is enhanced at structure and substructure scales, k{approx_equal}10{sup -2-0}h Mpc{sup -1}. Our smoking gun for discriminating this proposal from others with similar CMB and LSS predictions comes from correlations between cosmic shear and temperature anisotropies, which here indicate a noninflationary channel of contribution to LSS, with unique ringing features of nonlocal entanglement displayed at structure and substructure scales.