Chiral Symmetry and Neutrino Pion Production off the Nucleon

The neutrino pion production off the nucleon is traditionally described in the literature by means of the weak excitation of the Delta(1232) resonance and its subsequent decay into N pi. Here, we present results from a model that includes also some background terms required by chiral symmetry. We show that the contribution of these terms is sizeable and leads to significant effects in total and partially integrated pion production cross sections at intermediate energies of interest for neutrino oscillation experiments. Finally, we discuss parity-violating contributions to the pion angular differential cross section induced by the interference of these non-resonant terms with the Delta piece.Comment: To appear in the proceedings of 9th International Workshop On Neutrino Factories, Superbeams and Betabeams (NuFact07) August 6-11, 2007, Okayama University, Japa

Tachyon Vacuum in Cubic Superstring Field Theory

In this paper we give an exact analytic solution for tachyon condensation in the modified (picture 0) cubic superstring field theory. We prove the absence of cohomology and, crucially, reproduce the correct value for the D-brane tension. The solution is surprising for two reasons: First, the existence of a tachyon vacuum in this theory has not been definitively established in the level expansion. Second, the solution {\it vanishes} in the GSO$(-)$ sector, implying a ``tachyon vacuum'' solution exists even for a {\it BPS} D-brane.Comment: 16 pages, 2 figure

String Field Theory Vertices for Fermions of Integral Weight

We construct Witten-type string field theory vertices for a fermionic first order system with conformal weights (0,1) in the operator formulation using delta-function overlap conditions as well as the Neumann function method. The identity, the reflector and the interaction vertex are treated in detail paying attention to the zero mode conditions and the U(1) charge anomaly. The Neumann coefficients for the interaction vertex are shown to be intimately connected with the coefficients for bosons allowing a simple proof that the reparametrization anomaly of the fermionic first order system cancels the contribution of two real bosons. This agrees with their contribution c=-2 to the central charge. The overlap equations for the interaction vertex are shown to hold. Our results have applications in N=2 string field theory, Berkovits' hybrid formalism for superstring field theory, the \eta\xi-system and the twisted bc-system used in bosonic vacuum string field theory.Comment: 1+28 pages, minor improvements, references adde

Superstring field theory equivalence: Ramond sector

We prove that the finite gauge transformation of the Ramond sector of the modified cubic superstring field theory is ill-defined due to collisions of picture changing operators. Despite this problem we study to what extent could a bijective classical correspondence between this theory and the (presumably consistent) non-polynomial theory exist. We find that the classical equivalence between these two theories can almost be extended to the Ramond sector: We construct mappings between the string fields (NS and Ramond, including Chan-Paton factors and the various GSO sectors) of the two theories that send solutions to solutions in a way that respects the linearized gauge symmetries in both sides and keeps the action of the solutions invariant. The perturbative spectrum around equivalent solutions is also isomorphic. The problem with the cubic theory implies that the correspondence of the linearized gauge symmetries cannot be extended to a correspondence of the finite gauge symmetries. Hence, our equivalence is only formal, since it relates a consistent theory to an inconsistent one. Nonetheless, we believe that the fact that the equivalence formally works suggests that a consistent modification of the cubic theory exists. We construct a theory that can be considered as a first step towards a consistent RNS cubic theory.Comment: v1: 24 pages. v2: 27 pages, significant modifications of the presentation, new section, typos corrected, references adde

Cosmological tachyon from cubic string field theory

The classical dynamics of the tachyon scalar field of cubic string field theory is considered on a cosmological background. Starting from a nonlocal action with arbitrary tachyon potential, which encodes the bosonic and several supersymmetric cases, we study the equations of motion in the Hamilton-Jacobi formalism and with a generalized Friedmann equation, appliable in braneworld or modified gravity models. The cases of cubic (bosonic) and quartic (supersymmetric) tachyon potential in general relativity are automatically included. We comment the validity of the slow-roll approximation, the stability of the cosmological perturbations, and the relation between this tachyon and the Dirac-Born-Infeld one.Comment: 20 pages JHEP style, 1 figure; v4: misprints corrected, matches the published versio

Agile Detection of Delayed Gamma-Ray Emission from the Short Gamma-Ray Burst GRB 090510

Short gamma-ray bursts (GRBs), typically lasting less than 2 s, are a special class of GRBs of great interest. We report the detection by the AGILE satellite of the short GRB 090510 which shows two clearly distinct emission phases: a prompt phase lasting ~ 200 msec and a second phase lasting tens of seconds. The prompt phase is relatively intense in the 0.3-10 MeV range with a spectrum characterized by a large peak/cutoff energy near 3 MeV, in this phase, no significant high-energy gamma-ray emission is detected. At the end of the prompt phase, intense gamma-ray emission above 30 MeV is detected showing a power-law time decay of the flux of the type t^-1.3 and a broad-band spectrum remarkably different from that of the prompt phase. It extends from sub-MeV to hundreds of MeV energies with a photon index alpha ~ 1.5. GRB 090510 provides the first case of a short GRB with delayed gamma-ray emission. We present the timing and spectral data of GRB 090510 and briefly discuss its remarkable properties within the current models of gamma-ray emission of short GRBs.Comment: Accepted by the Astrophysical Journal Letters on September 11, 200

Bosonic D-brane Effective Action in Linear Dilaton Background

In this paper we will study tachyon effective action for Dp-brane in bosonic string theory in the linear dilaton background. We obtain the tachyon effective Lagrangian from boundary state coeficient of Dp-brane in the linear dilaton background and compare it with tachyon effective Lagrangians that were proposed in previous papers.Comment: 16 pages, Typos correcte

Abelian and nonabelian vector field effective actions from string field theory

The leading terms in the tree-level effective action for the massless fields of the bosonic open string are calculated by integrating out all massive fields in Witten's cubic string field theory. In both the abelian and nonabelian theories, field redefinitions make it possible to express the effective action in terms of the conventional field strength. The resulting actions reproduce the leading terms in the abelian and nonabelian Born-Infeld theories, and include (covariant) derivative corrections.Comment: 49 pages, 1 eps figur

Finite Temperature Systems of Brane-Antibrane on a Torus

In order to study the thermodynamic properties of brane-antibrane systems in the toroidal background, we compute the finite temperature effective potential of tachyon T in this system on the basis of boundary string field theory. We first consider the case that all the radii of the target space torus are about the string scale. If the Dp-antiDp pair is extended in all the non-compact directions, the sign of the coefficient of |T|^2 term of the potential changes slightly below the Hagedorn temperature. This means that a phase transition occurs near the Hagedorn temperature. On the other hand, if the Dp-antiDp pair is not extended in all the non-compact directions, the coefficient is kept negative, and thus a phase transition does not occur. Secondly, we consider the case that some of the radii of the target space torus are much larger than the string scale and investigate the behavior of the potential for each value of the radii and the total energy. If the Dp-antiDp pair is extended in all the non-compact directions, a phase transition occurs for large enough total energy.Comment: 23 pages, 3 figures, minor errors corrected, version to appear in JHE