812 research outputs found
SV-map between Type I and Heterotic Sigma Models
The scattering amplitudes of gauge bosons in heterotic and open superstring
theories are related by the single-valued projection which yields heterotic
amplitudes by selecting a subset of multiple zeta value coefficients in the
(string tension parameter) expansion of open string amplitudes. In
the present work, we argue that this relation holds also at the level of
low-energy expansions (or individual Feynman diagrams) of the respective
effective actions, by investigating the beta functions of two-dimensional sigma
models describing world-sheets of open and heterotic strings. We analyze the
sigma model Feynman diagrams generating identical effective action terms in
both theories and show that the heterotic coefficients are given by the
single-valued projection of the open ones. The single-valued projection appears
as a result of summing over all radial orderings of heterotic vertices on the
complex plane representing string world-sheet.Comment: 28 page
An effectual template bank for the detection of gravitational waves from inspiralling compact binaries with generic spins
We report the construction of a three-dimensional template bank for the
search for gravitational waves from inspiralling binaries consisting of
spinning compact objects. The parameter space consists of two dimensions
describing the mass parameters and one "reduced-spin" parameter, which
describes the secular (non-precessing) spin effects in the waveform. The
template placement is based on an efficient stochastic algorithm and makes use
of the semi-analytical computation of a metric in the parameter space. We
demonstrate that for "low-mass" () binaries,
this template bank achieves effective fitting factors --
towards signals from generic spinning binaries in the advanced detector era
over the entire parameter space of interest (including binary neutron stars,
binary black holes, and black hole-neutron star binaries). This provides a
powerful and viable method for searching for gravitational waves from generic
spinning low-mass compact binaries. Under the assumption that spin magnitudes
of black-holes [neutron-stars] are uniformly distributed between 0--0.98 [0 --
0.4] and spin angles are isotropically distributed, the expected improvement in
the average detection volume (at a fixed signal-to-noise-ratio threshold) of a
search using this reduced-spin bank is , as compared to a search
using a non-spinning bank.Comment: Minor changes, version appeared in Phys. Rev.
Current Exchanges for Reducible Higher Spin Modes on AdS
We show how to decompose a Lagrangian for reducible massless bosonic Higher Spin modes into the ones describing irreducible (Fronsdal) Higher Spin modes on a D dimensional AdS space. Using this decomposition we construct a new nonabelian cubic interaction vertex for reducible higher spin modes and two scalars on AdS from the already known vertex which involves irreducible (Fronsdal) mode
On manifolds admitting the consistent Lagrangian formulation for higher spin fields
We study a possibility of Lagrangian formulation for free higher spin bosonic
totally symmetric tensor field on the background manifold characterizing by the
arbitrary metric, vector and third rank tensor fields in framework of BRST
approach. Assuming existence of massless and flat limits in the Lagrangian and
using the most general form of the operators of constraints we show that the
algebra generated by these operators will be closed only for constant curvature
space with no nontrivial coupling to the third rank tensor and the strength of
the vector fields. This result finally proves that the consistent Lagrangian
formulation at the conditions under consideration is possible only in constant
curvature Riemann space.Comment: 11 pages; v2: minor typos corrected, a reference adde
On gravitational couplings in D-brane action
We compute the two closed string graviton - two open string scalar scattering
amplitude on the disc to show that there is no second-derivative curvature -
scalar coupling term R X^2 in the low-energy effective action of a D-brane in
curved space in type II superstring theory.Comment: 15 pages, 1 figure, LaTex JHEP style; v2: reference added, typos
corrected; v3: section 2 rewritten due to an error in gauge fixing, appendix
added, conclusions unchange
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