String production after angled brane inflation

We describe string production after angled brane inflation. First, we point out that there was a discrepancy in previous discussions. The expected tension of the cosmic string calculated from the four-dimensional effective Lagrangian did not match the one obtained in the brane analysis. In the previous analysis, the cosmic string is assumed to correspond to the lower-dimensional daughter brane, which wraps the same compactified space as the original mother brane. In this case, however, the tension of the daughter brane cannot depend on the angle (\theta). On the other hand, from the analysis of the effective Lagrangian for tachyon condensation, it is easy to see that the tension of the cosmic string must be proportional to \theta, when \theta << 1. This is an obvious discrepancy that must be explained by consideration of the explicit brane dynamics. In this paper, we will solve this problem by introducing a simple idea. We calculate the tension of the string in the two cases, which matches precisely. The cosmological constraint for angled inflation is relaxed, because the expected tension of the cosmic string becomes smaller than the one obtained in previous arguments, by a factor of \theta.Comment: 13pages, 3 figures, typos correcte

Test evaluation of fuel cell catalysts Quarterly report, Aug. 16 - Nov. 15, 1967

Corrosion testing of nickel, cobalt, nickel cobalt alloy, borides, and other fuel cell catalyst samples for activity in oxidation of hydrazin

Q ball inflation

We show that inflation can occur in the core of a Q-ball.Comment: 11 pages, latex2e, no figure, references added, final version to appear in PR

Formation of monopoles and domain walls after brane inflation

We study cosmological defect formation after brane inflation. The cosmological defects are corresponding to the branes that have less than three spacial dimensions in the uncompactified spacetime. Contrary to the previous arguments, production of monopoles and domain walls are not always negligible. Monopoles and domain walls are formed by the branes extended between mother branes.Comment: 27pages, 7 figures, many comments, footnotes and reviews are added, to appear in JHE

Dark matter production from cosmic necklaces

Cosmic strings have gained a great interest, since they are formed in a large class of brane inflationary models. The most interesting story is that cosmic strings in brane models are distinguished in future cosmological observations. If the strings in brane models are branes or superstrings that can move along compactified space, and also if there are degenerated vacua along the compactified space, kinks interpolate between degenerated vacua become ``beads'' on the strings. In this case, strings turn into necklaces. In the case that the compact manifold in not simply connected, a string loop that winds around a nontrivial circle is stable due to the topological reason. Since the existence of the (quasi-)degenerated vacua and the nontrivial circle is a common feature of the brane models, it is important to study cosmological constraints on the cosmic necklaces and the stable winding states. In this paper, we consider dark matter production from loops of the cosmic necklaces. Our result suggests that necklaces can put stringent bound on certain kinds of brane models.Comment: 27 pages, 5 figures, added many comments and 3 figures, accepted for publication in JCA

Test evaluation of fuel cell catalysts Quarterly report, 15 Feb. - 15 May 1967

Catalytic activity of iron compounds for fuel cell catalyst

Magnetic-field-induced chiral hidden order in URu2Si2

Two of the most striking and yet unresolved manifestations of the hidden order (HO) in URu2Si2, are associated on one hand with the double-step metamagnetic transitions and on the other with the giant anomalous Nernst signal. Both are observed when a magnetic field is applied along the c-axis. Here we provide for the first time a unified understanding of these puzzling phenomena and the related field-temperature (B-T) phase diagram. We demonstrate that the HO phase at finite fields can be explained with a chiral dxy+idx2-y2 spin density wave, assuming that the zero field HO contains only the time-reversal symmetry preserving idx2-y2 component. We argue that the presence of the field-induced chiral HO can be reflected in a distinctive non-linear B-dependence of the Kerr angle, when a Kerr experiment is conducted for finite fields. This fingerprint can be conclusive for the possible emergence of chirality in the HO.Comment: 8 pages and 9 figures main text + 6 pages supplementary material. Philosophical Magazine: Special Issue: Focused Issue on Hidden Order in URu2Si2 (May 2014

Evolution of curvature perturbation in generalized gravity theories

Using the cosmological perturbation theory in terms of the delta-N formalism, we find the simple formulation of the evolution of the curvature perturbation in generalized gravity theories. Compared with the standard gravity theory, a crucial difference appears in the end-boundary of the inflationary stage, which is due to the non-ideal form of the energy momentum tensor that depends explicitly on the curvature scalar. Recent study shows that ultraviolet-complete quantum theory of gravity may be approximated by using a generalized gravity action. Our paper may give an important step in understanding the evolution of the curvature perturbation during inflation, where the energy momentum tensor may not be given by the ideal form due to the corrections from the fundamental theory.Comment: 15pages, fixed references, accepted for publication in CQ

Hall conductance of a pinned vortex lattice in a high magnetic field

We calculate the quasiparticle contribution to the zero temperature Hall conductance of two-dimensional extreme type-II superconductors in a high magnetic field, using the Landau basis. As one enters the superconducting phase the Hall conductance is renormalized to smaller values, with respect to the normal state result, until a quantum level-crossing transition is reached. At high values of the order parameter, where the quasiparticles are bound to the vortex cores, the Hall conductance is expected to tend to zero due to a theorem of Thouless.Comment: To appear in Journ. Phys. : Cond. Matte