Numerical evaluation of gauge invariants for a-gauge solutions in open string field theory
We evaluate gauge invariants (the action and the gauge-invariant overlap) for numerical solutions satisfying the “a-gauge” condition with various values of a in the cubic open bosonic string field theory. We use the level-truncation approximation and an iterative procedure to construct numerical solutions in the twist-even universal space. The resulting gauge invariants are numerically stable and almost equal to those of Schnabl’s solution for tachyon condensation. Our result provides further evidence that these numerical and analytic solutions are gauge equivalent.

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: 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: 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: 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: 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: Probing quintessence potential with future cosmological surveys
abstract: Quintessence, a scalar field model, has been proposed to account for the acceleration of the Universe at present. We discuss how accurately quintessence models are discriminated by future cosmological surveys, which include experiments of CMB, galaxy clustering, weak lensing, and the type Ia SNe surveys, by making use of the conventional parameterized dark energy models. We can see clear differences between the thawing and the freezing quintessence models at more than 1σ (2σ) confidence level as long as the present equation of state for quintessence is away from -1 as wX−0.95(−0.90). However, it is found to be difficult to probe the effective mass squared for the potential in thawing models, whose signs are different between the quadratic and the cosine-type potentials. This fact may require us to invent a new estimator to distinguish quintessence models beyond the thawing and the freezing ones.

title: Affleck-Dine baryogenesis with R-parity violation
abstract: We investigate whether the baryon asymmetry of the universe is explained in the framework of the supersymmetric extension of the Standard Model with R-parity violating interactions. It is shown that the Affleck-Dine mechanism naturally works via a trilinear interaction $LLE^c$, $LQD^c$, or $U^cD^cD^c$, if the magnitude of the coupling corresponding to the operator $\lambda$, $\lambda'$, or $\lambda''$ is sufficiently small. The formation of Q-balls and their subsequent evolution are also discussed. The present baryon asymmetry can be explained in the parameter region where R-parity is mildly violated $10^{-9}\lesssim\lambda,\lambda',\lambda''\lesssim 10^{-6}$ and the mass of the gravitino is relatively heavy $m_{3/2}\gtrsim 10^4\mathrm{GeV}$. On the other hand, it is difficult to explain the present baryon asymmetry for larger values of R-parity violating couplings $\lambda,\lambda',\lambda''\gtrsim 10^{-5}$, since Q-balls are likely to be destructed in the thermal environment and the primordial baryon number is washed away.

title: Higher order corrections to the primordial gravitational wave spectrum and its impact on parameter estimates for inflation
abstract: We study the impact of the use of the power series expression for the primordial tensor spectrum on parameter estimation from future direct detection gravitational wave experiments. The spectrum approximated by the power series expansion may give large deviation from the true (fiducial) value when it is normalized at CMB scale because of the large separation between CMB and direct detection scales. We derive the coefficients of the higher order terms of the expansion up to the sixth order within the framework of the slow-roll approximation and investigate how well the inclusion of higher order terms improves the analytic prediction of the spectrum amplitude by comparing with numerical results. Using the power series expression, we consider future constraints on inflationary parameters expected from direct detection experiments of the inflationary gravitational wave background and show that the truncation of the higher order terms can lead to incorrect evaluation of the parameters. We present two example models; a quadratic chaotic inflation model and mixed inflaton and curvaton model with a quartic inflaton potential.

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: 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.