2,359 research outputs found
Non semi-simple sl(2) quantum invariants, spin case
Invariants of 3-manifolds from a non semi-simple category of modules over a
version of quantum sl(2) were obtained by the last three authors in
[arXiv:1404.7289]. In their construction the quantum parameter is a root of
unity of order where is odd or congruent to modulo . In this
paper we consider the remaining cases where is congruent to zero modulo
and produce invariants of -manifolds with colored links, equipped with
generalized spin structure. For a given -manifold , the relevant
generalized spin structures are (non canonically) parametrized by
.Comment: 13 pages, 16 figure
High-order half-integral conservative post-Newtonian coefficients in the redshift factor of black hole binaries
The post-Newtonian approximation is still the most widely used approach to
obtaining explicit solutions in general relativity, especially for the
relativistic two-body problem with arbitrary mass ratio. Within many of its
applications, it is often required to use a regularization procedure. Though
frequently misunderstood, the regularization is essential for waveform
generation without reference to the internal structure of orbiting bodies. In
recent years, direct comparison with the self-force approach, constructed
specifically for highly relativistic particles in the extreme mass ratio limit,
has enabled preliminary confirmation of the foundations of both computational
methods, including their very independent regularization procedures, with high
numerical precision. In this paper, we build upon earlier work to carry this
comparison still further, by examining next-to-next-to-leading order
contributions beyond the half integral 5.5PN conservative effect, which arise
from terms to cubic and higher orders in the metric and its multipole moments,
thus extending scrutiny of the post-Newtonian methods to one of the highest
orders yet achieved. We do this by explicitly constructing tail-of-tail terms
at 6.5PN and 7.5PN order, computing the redshift factor for compact binaries in
the small mass ratio limit, and comparing directly with numerically and
analytically computed terms in the self-force approach, obtained using
solutions for metric perturbations in the Schwarzschild space-time, and a
combination of exact series representations possibly with more typical PN
expansions. While self-force results may be relativistic but with restricted
mass ratio, our methods, valid primarily in the weak-field slowly-moving
regime, are nevertheless in principle applicable for arbitrary mass ratios.Comment: 33 pages, no figure; minor correction
Half-integral conservative post-Newtonian approximations in the redshift factor of black hole binaries
Recent perturbative self-force computations (Shah, Friedman & Whiting,
submitted to Phys. Rev. {\bf D}, arXiv:1312.1952 [gr-qc]), both numerical and
analytical, have determined that half-integral post-Newtonian terms arise in
the conservative dynamics of black-hole binaries moving on exactly circular
orbits. We look at the possible origin of these terms within the post-Newtonian
approximation, find that they essentially originate from non-linear
"tail-of-tail" integrals and show that, as demonstrated in the previous paper,
their first occurrence is at the 5.5PN order. The post-Newtonian method we use
is based on a multipolar-post-Minkowskian treatment of the field outside a
general matter source, which is re-expanded in the near zone and extended
inside the source thanks to a matching argument. Applying the formula obtained
for generic sources to compact binaries, we obtain the redshift factor of
circular black hole binaries (without spins) at 5.5PN order in the extreme mass
ratio limit. Our result fully agrees with the determination of the 5.5PN
coefficient by means of perturbative self-force computations reported in the
previously cited paper.Comment: 18 pages, no figures, references updated and minor corrections
include
Hadamard Regularization
Motivated by the problem of the dynamics of point-particles in high
post-Newtonian (e.g. 3PN) approximations of general relativity, we consider a
certain class of functions which are smooth except at some isolated points
around which they admit a power-like singular expansion. We review the concepts
of (i) Hadamard ``partie finie'' of such functions at the location of singular
points, (ii) the partie finie of their divergent integral. We present and
investigate different expressions, useful in applications, for the latter
partie finie. To each singular function, we associate a partie-finie (Pf)
pseudo-function. The multiplication of pseudo-functions is defined by the
ordinary (pointwise) product. We construct a delta-pseudo-function on the class
of singular functions, which reduces to the usual notion of Dirac distribution
when applied on smooth functions with compact support. We introduce and analyse
a new derivative operator acting on pseudo-functions, and generalizing, in this
context, the Schwartz distributional derivative. This operator is uniquely
defined up to an arbitrary numerical constant. Time derivatives and partial
derivatives with respect to the singular points are also investigated. In the
course of the paper, all the formulas needed in the application to the physical
problem are derived.Comment: 50 pages, to appear in Journal of Mathematical Physic
Multipole expansion at the level of the action
Sources of long wavelength radiation are naturally described by an effective
field theory (EFT) which takes the form of a multipole expansion. Its action is
given by a derivative expansion where higher order terms are suppressed by
powers of the ratio of the size of the source over the wavelength. In order to
determine the Wilson coefficients of the EFT, i.e. the multipole moments, one
needs the mapping between a linear source term action and the multipole
expansion form of the action of the EFT. In this paper we perform the multipole
expansion to all orders by Taylor expanding the field in the source term and
then decomposing the action into symmetric trace free tensors which form
irreducible representations of the rotation group. We work at the level of the
action, and we obtain the action to all orders in the multipole expansion and
the exact expressions for the multipole moments for a scalar field,
electromagnetism and linearized gravity. Our results for the latter two cases
are manifestly gauge invariant. We also give expressions for the energy flux
and the (gauge dependent) radiation field to all orders in the multipole
expansion. The results for linearized gravity are a component of the EFT
framework NRGR and will greatly simplify future calculations of gravitational
wave observables in the radiation sector of NRGR.Comment: 39 pages, some typos corrected, published versio
Efficient Enumeration of Non-Equivalent Squares in Partial Words with Few Holes
International audienceA partial word is a word with holes (also called don't cares: special symbols which match any symbol). A p-square is a partial word matching at least one standard square without holes (called a full square). Two p-squares are called equivalent if they match the same sets of full squares. Denote by psquares(T) the number of non-equivalent p-squares which are subwords of a partial word T. Let PSQUARES k (n) be the maximum value of psquares(T) over all partial words of length n with k holes. We show asympthotically tight bounds: c1 · min(nk 2 , n 2) ≤ PSQUARES k (n) ≤ c2 · min(nk 2 , n 2) for some constants c1, c2 > 0. We also present an algorithm that computes psquares(T) in O(nk 3) time for a partial word T of length n with k holes. In particular, our algorithm runs in linear time for k = O(1) and its time complexity near-matches the maximum number of non-equivalent p-squares
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