364 research outputs found
Covariant Quantization of Superstrings Without Pure Spinor Constraints
We construct a covariant quantum superstring, extending Berkovits' approach
by introducing new ghosts to relax the pure spinor constraints. The central
charge of the underlying Kac-Moody algebra, which would lead to an anomaly in
the BRST charge, is treated as a new generator with a new b-c system. We
construct a nilpotent BRST current, an anomalous ghost current and an
anomaly-free energy-momentum tensor. For open superstrings, we find the correct
massless spectrum. In addition, we construct a Lorentz invariant B-field to be
used for the computation of the integrated vertex operators and amplitudes.Comment: 30 page
Four dimensional "old minimal" N=2 supersymmetrization of R^4
We write in superspace the lagrangian containing the fourth power of the Weyl
tensor in the "old minimal" d=4, N=2 supergravity, without local SO(2)
symmetry. Using gauge completion, we analyze the lagrangian in components. We
find out that the auxiliary fields which belong to the Weyl and compensating
vector multiplets have derivative terms and therefore cannot be eliminated
on-shell. Only the auxiliary fields which belong to the compensating nonlinear
multiplet do not get derivatives and could still be eliminated; we check that
this is possible in the leading terms of the lagrangian. We compare this result
to the similar one of "old minimal" N=1 supergravity and we comment on possible
generalizations to other versions of N=1,2 supergravity.Comment: 31 pages, no figures. Minor corrections. Details of the full
calculation included as an appendix. Reference adde
A twistor-like D=10 superparticle action with manifest N=8 world-line supersymmetry
We propose a new formulation of the Brink-Schwarz superparticle which
is manifestly invariant under both the target-space super-Poincar\'e group and
the world-line local superconformal group. This twistor-like construction
naturally involves the sphere as a coset space of the Lorentz
group. The action contains only a finite set of auxiliary fields, but they
appear in unusual trilinear combinations. The origin of the on-shell
fermionic symmetry of the standard Brink-Schwarz formulation is
explained. The coupling to a super-Maxwell background requires a new
mechanism, in which the electric charge appears only on shell as an integration
constant.Comment: 22pages, standard LATEX fil
A New First Class Algebra, Homological Perturbation and Extension of Pure Spinor Formalism for Superstring
Based on a novel first class algebra, we develop an extension of the pure
spinor (PS) formalism of Berkovits, in which the PS constraints are removed. By
using the homological perturbation theory in an essential way, the BRST-like
charge of the conventional PS formalism is promoted to a bona fide
nilpotent charge , the cohomology of which is equivalent to the
constrained cohomology of . This construction requires only a minimum number
(five) of additional fermionic ghost-antighost pairs and the vertex operators
for the massless modes of open string are obtained in a systematic way.
Furthermore, we present a simple composite "-ghost" field which
realizes the important relation , with the
Virasoro operator, and apply it to facilitate the construction of the
integrated vertex. The present formalism utilizes U(5) parametrization and the
manifest Lorentz covariance is yet to be achieved.Comment: 38 pages, no figure. Proof of triviality of delta-homology improved
and a reference adde
Ground and excited states Gamow-Teller strength distributions of iron isotopes and associated capture rates for core-collapse simulations
This paper reports on the microscopic calculation of ground and excited
states Gamow-Teller (GT) strength distributions, both in the electron capture
and electron decay direction, for Fe. The associated electron and
positron capture rates for these isotopes of iron are also calculated in
stellar matter. These calculations were recently introduced and this paper is a
follow-up which discusses in detail the GT strength distributions and stellar
capture rates of key iron isotopes. The calculations are performed within the
framework of the proton-neutron quasiparticle random phase approximation
(pn-QRPA) theory. The pn-QRPA theory allows a microscopic
\textit{state-by-state} calculation of GT strength functions and stellar
capture rates which greatly increases the reliability of the results. For the
first time experimental deformation of nuclei are taken into account. In the
core of massive stars isotopes of iron, Fe, are considered to be
key players in decreasing the electron-to-baryon ratio () mainly via
electron capture on these nuclide. The structure of the presupernova star is
altered both by the changes in and the entropy of the core material.
Results are encouraging and are compared against measurements (where possible)
and other calculations. The calculated electron capture rates are in overall
good agreement with the shell model results. During the presupernova evolution
of massive stars, from oxygen shell burning stages till around end of
convective core silicon burning, the calculated electron capture rates on
Fe are around three times bigger than the corresponding shell model
rates. The calculated positron capture rates, however, are suppressed by two to
five orders of magnitude.Comment: 18 pages, 12 figures, 10 table
Interconnections between type II superstrings, M theory and N=4 supersymmetric Yang--Mills
These lecture notes begin with a review of the first nonleading contributions
to the derivative expansion of the M theory effective action compactified on a
two-torus. The form of these higher-derivative interactions is shown to follow
from ten-dimensional type IIB supersymmetry as well as from one-loop quantum
corrections to classical eleven-dimensional supergravity. The detailed
information concerning D-instanton effects encoded in these terms is related to
the problem of evaluating the Witten index for D-particles in the type IIA
theory. Using the AdS/CFT conjecture, it also leads to very specific
predictions of multi-instanton contributions in supersymmetric SU(N)
Yang--Mills theory in the limit of strong 't Hooft coupling. [Extended version
of lectures given at 22nd Johns Hopkins Workshop (Gothenberg, August 20-22
1998); `Quantum Aspects of Gauge Theories, Supersymmetry and Unification', TMR
meeting (Corfu, September 20-26 1998); Andrjewski lectures (Berlin, November
1-6 1998).]Comment: 80 pages, LaTe
Relating Green-Schwarz and Extended Pure Spinor Formalisms by Similarity Transformation
In order to gain deeper understanding of pure-spinor-based formalisms of
superstring, an explicit similarity transformation is constructed which
provides operator mapping between the light-cone Green-Schwarz (LCGS) formalism
and the extended pure spinor (EPS) formalism, a recently proposed
generalization of the Berkovits' formalism in an enlarged space. By applying a
systematic procedure developed in our previous work, we first construct an
analogous mapping in the bosonic string relating the BRST and the light-cone
formulations. This provides sufficient insights and allows us to construct the
desired mapping in the more intricate case of superstring as well. The success
of the construction owes much to the enlarged field space where pure spinor
constraints are removed and to the existence of the ``B-ghost'' in the EPS
formalism.Comment: 37pages, no figur
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