Non-Gaussianity and baryonic isocurvature fluctuations in the curvaton scenario
We discuss non-Gaussianity and baryonic isocurvature fluctuations in the curvaton scenario, assuming that the baryon asymmetry of the universe originates only from the decay products of the inflaton. When large non-Gaussianity is realized in such a scenario, non-vanishing baryonic isocurvature fluctuations can also be generated unless the baryogenesis occurs after the decay of the curvaton. We calculate the non-linearity parameter f NL and the baryonic isocurvature fluctuations, taking account of the primordial fluctuations of both the inflaton and the curvaton. We show that, although current constraints on isocurvature fluctuations are severe, the non-linearity parameter can be large as f NL ∼ O ( 10 – 100 ) without conflicting with the constraints.

title: Primordial Helium Abundance from CMB: a constraint from recent observations and a forecast
abstract: We studied a constraint on the primordial helium abundance Y{sub p} from current and future observations of CMB. Using the currently available data from WMAP, ACBAR, CBI, and BOOMERANG, we obtained the constraint as Y{sub p}=0.25{sub -0.07}{sup +0.10} at 68% confidence level. We also provide a forecast for the Planck experiment using the Markov chain Monte Carlo approach. In addition to forecasting the constraint on Y{sub p}, we investigate how assumptions for Y{sub p} affect constraints on the other cosmological parameters.

title: Robustness and predictivity of 4 TeV unification
abstract: The stability of the predictions of two of the standard model parameters, α 3 ( M Z ) and sin 2 θ ( M Z ), in a M U ∼4 TeV unification model is examined. It is concluded that varying the unification scale between M U ≃2.5 TeV and M U ≃5 TeV leaves robust all predictions within reasonable bounds. Choosing M U =3.8±0.4 TeV gives, at lowest order, accurate predictions at M Z . The impact of threshold effects on unification depends on the spectrum of states beyond the standard model.

title: On the determination of neutrino masses and dark energy evolution from the cross-correlation of CMB and LSS
abstract: We discuss the possibilities of the simultaneous determination of the neutrino masses and the evolution of dark energy from future cosmological observations such as cosmic microwave background (CMB), large scale structure (LSS) and the cross-correlation between them. Recently it has been discussed that there is a degeneracy between the neutrino masses and the equation of state for dark energy. It is also known that there are some degeneracies among the parameters describing the dark energy evolution. We discuss the implications of these for the cross-correlation of CMB with LSS in some detail. Then we consider to what extent we can determine the neutrino masses and the dark energy evolution using the expected data from CMB, LSS and their cross-correlation.

title: Correlated Isocurvature Fluctuation of Quintessence and Curvaton Scenario
abstract: We consider cosmic microwave background (CMB) anisotropy in models with quintessence taking into account of isocurvature fluctuation in the quintessence. It is shown that, if the primordial fluctuation of the quintessence has a correlation with the adiabatic density fluctuations, CMB angular power spectrum $C_l$ at low multipoles can be suppressed. Possible scenario of generating correlated mixture of the quintessence and adiabatic fluctuations is also discussed.

title: Mixed inflaton and spectator field models after Planck
abstract: We investigate the possibility that the primordial perturbation has two sources: the inflaton and a spectator field, which is not dynamically important during inflation but which after inflation can contribute to the curvature perturbation. We derive the constraints on the model by using recent Planck results on the spectral index, tensor-to-scalar ratio and nonlinearity parameters fNL and τNL for the cases with and without specifying the inflation and spectator models. If one chooses the spectator to be the curvaton with a quadratic potential, non-Gaussianities can be computed and imply restrictions on possible values of the ratio of the spectator-to-inflaton power R. We also consider a mixed curvaton and chaotic inflation model and show that even quartic chaotic inflation is still feasible in the context of mixed models even with Planck data.

title: Open string field theory on noncommutative space
abstract: We study Witten's open string field theory in the presence of a constant B field. We construct the string field theory in the operator formalism and find that, compared to the ordinary theory with no B field, the vertices in the resulting theory has an additional factor. The factor makes the zero modes of strings noncommutative. This is in agreement with the results in the first-quantized formulation. We also discuss background independence of the purely cubic action derived from the above string field theory and then find a redefinition of string fields to remove the additional factor from the vertex. Furthermore, we briefly discuss the supersymmetric extension of our string field theory.

title: Homotopy operators and identity-based solutions in cubic superstring field theory
abstract: 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: Classical Solutions and Order of Zeros in Open String Field Theory
abstract: Earlier an analytic approach is proposed for classical solutions describing tachyon vacuum in open string field theory. Based on the approach, we construct a certain class of classical solutions written in terms of holomorphic functions with higher order zeros. Taking the simplest among the new classical solutions, we study the cohomology of the new BRS charge and make a numerical analysis of the vacuum energy. The results indicate that the new non-trivial solution is another analytic candidate for the tachyon vacuum.

title: Dilaton Condensation in Cubic Open String Field Theory
abstract: We construct an exact and finite classical solution in cubic open string field theory. The classical solution has a well-defined Fock space expression. Through the redefinition of a string field, the string field theory expanded around the classical solution can be transformed into the theory with a different coupling constant, where other backgrounds are unchanged. Therefore, the classical solution represents the condensation of the dilaton in cubic open string field theory. E-mail address: tomo@asuka.phys.nara-wu.ac.jp E-mail address:

title: Schnabl's Solution and Boundary States in Open String Field Theory
abstract: We discuss that Schnabl's solution is an off-shell extension of the boundary state describing a D-brane in the closed string sector. It gives the physical meaning of the gauge-invariant overlaps for the solution in our previous paper and supports Ellwood's recent proposal in the operator formalism.