307 research outputs found
A Covariant Action with a Constraint and Feynman Rules for Fermions in Open Superstring Field Theory
In a way analogous to type IIB supergravity, we give a covariant action for
the fermion field supplemented with a constraint which should be imposed on
equations of motion, in Berkovits' open superstring field theory. From this
action we construct Feynman rules for computing perturbative amplitudes for
fermions. We show that on-shell tree level 4-point amplitudes computed by using
these rules coincide with those of the first quantization formalism.Comment: LaTeX, 14 pages, 4 figure
Field Redefinitions, T-duality and Solutions in Closed String Field Theories
We investigate classical solutions in closed bosonic string field theory and
heterotic string field theory that are obtained order by order starting from
solutions of the linearized equations of motion, and we discuss the ``field
redefinitions'' which relate massless fields in the string field theory side
and the low energy effective theory side. Massless components of the string
field theory solutions are not corrected and from them we can infer
corresponding solutions in the effective theory: the chiral null model and the
pp-wave solution with B-field, which have been known to be alpha'-exact. These
two sets of solutions in the two sides look slightly different because of the
field redefinitions. It turns out that T-duality is a useful tool to determine
them: We show that some part of the field redefinitions can be determined by
using the correspondence between T-duality rules in the two sides, irrespective
of the detail of the interaction terms and the integrating-out procedure.
Applying the field redefinitions, we see that the solutions in the effective
theory side are reproduced from the string field theory solutions.Comment: LaTeX, 40 pages, no figure v2: minor corrections v3: minor correctio
Kappa symmetric OSp(2|2) WZNW model
We construct a kappa symmetric WZNW model for the OSp(2|2) supergroup, whose
bosonic part is AdS3xS1 space. The field equation gives the chiral current
conservation and the right/left factorization is shown after the kappa symmetry
is fixed. The right-moving modes contain both bosons and fermions while the
left-moving modes contain only bosons.Comment: 18 pages; reference and comments added, version to appear in JHE
Analytical Tachyonic Lump Solutions in Open Superstring Field Theory
We construct a classical solution in the GSO(-) sector in the framework of a
Wess-Zumino-Witten-like open superstring field theory on a non-BPS D-brane. We
use an su(2) supercurrent, which is obtained by compactifying a direction to a
circle with the critical radius, in order to get analytical tachyonic lump
solutions to the equation of motion. By investigating the action expanded
around a solution we find that it represents a deformation from a non-BPS
D-brane to a D-brane-anti-D-brane system at the critical value of a parameter
which is contained in classical solutions. Although such a process was
discussed in terms of boundary conformal field theory before, our study is
based on open superstring field theory including interaction terms.Comment: 17 pages, references adde
On factorizations in perturbative quantum gravity
Some features of Einstein gravity are most easily understood from string
theory but are not manifest at the level of the usual Lagrangian formulation.
One example is the factorization of gravity amplitudes into gauge theory
amplitudes. Based on the recently constructed `double field theory' and a
geometrical frame-like formalism developed by Siegel, we provide a framework of
perturbative Einstein gravity coupled to a 2-form and a dilaton in which, as a
consequence of T-duality, the Feynman rules factorize to all orders in
perturbation theory. We thereby establish the precise relation between the
field variables in different formulations and discuss the Lagrangian that, when
written in terms of these variables, makes a left-right factorization manifest.Comment: 18 pages, v2: reference added, to appear in JHE
Development of Ray Tracing Algorithms for Scanning Plane and Transverse Plane Analysis for Satellite Multibeam Application
Reflector antennas have been widely used in many areas. In the implementation of parabolic reflector antenna for broadcasting satellite applications, it is essential for the spacecraft antenna to provide precise contoured beam to effectively serve the required region. For this purpose, combinations of more than one beam are required. Therefore, a tool utilizing ray tracing method is developed to calculate precise off-axis beams for multibeam antenna system. In the multibeam system, each beam will be fed from different feed positions to allow the main beam to be radiated at the exact direction on the coverage area. Thus, detailed study on caustics of a parabolic reflector antenna is performed and presented in this paper, which is to investigate the behaviour of the rays and its relation to various antenna parameters. In order to produce accurate data for the analysis, the caustic behaviours are investigated in two distinctive modes: scanning plane and transverse plane. This paper presents the detailed discussions on the derivation of the ray tracing algorithms, the establishment of the equations of caustic loci, and the verification of the method through calculation of radiation pattern
String solitons in the M5-brane worldvolume with a Nambu-Poisson structure and Seiberg-Witten map
We analyze BPS equations for string-like configurations derived from the
M5-brane worldvolume action with a Nambu-Poisson structure constructed in
arXiv:0804.3629, arXiv:0805.2898. We solve the BPS equations up to the first
order in the parameter which characterizes the strength of the
Nambu-Poisson bracket. We compare our solutions to previously constructed BPS
string solitons in the conventional description of M5-brane in a constant
three-form background via Seiberg-Witten map, and find agreement.Comment: v2: minor corrections, the title slightly changed. 10 pages. v3: some
clarifying comment
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
BPS States on M5-brane in Large C-field Background
We extensively study BPS solutions of the low energy effective theory of
M5-brane in large C-field background. This provides us an opportunity to
explore the interactions turned on by C-field background through the
Nambu-Poisson structure. The BPS states considered in this paper include the
M-waves, the self-dual string (M2 ending on M5), tilted M5-brane, holomorphic
embedding of M5-brane and the intersection of two M5-branes along a 3-brane.Comment: 25 pages, reference adde
D-branes in PP-Waves and Massive Theories on Worldsheet with Boundary
We investigate the supersymmetric D-brane configurations in the pp-wave
backgrounds proposed by Maldacena and Maoz. We study the surviving
supersymmetry in a D-brane configuration from the worldvolume point of view.
When we restrict ourselves to the background with N=(2,2) supersymmetry and no
holomorphic Killing vector term, there are two types of supersymmetric
D-branes: A-type and B-type. An A-type brane is wrapped on a special Lagrangian
submanifold, and the imaginary part of the superpotential should be constant on
its worldvolume. On the other hand, a B-type brane is wrapped on a complex
submanifold, and the superpotential should be constant on its worldvolume. The
results are almost consistent with the worldsheet theory in the lightcone
gauge. The inclusion of gauge fields is also discussed and found BPS D-branes
with the gauge field excitations. Furthermore, we consider the backgrounds with
holomorphic Killing vector terms and N=(1,1) supersymmetric backgrounds.Comment: 27 pages, LaTeX, no figure. v2: typos corrected, comments added,
references added. v3: typos corrected, comments added, references added.
v4:typos correcte
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