19,452 research outputs found

### High accuracy simulations of black hole binaries:spins anti-aligned with the orbital angular momentum

High-accuracy binary black hole simulations are presented for black holes
with spins anti-aligned with the orbital angular momentum. The particular case
studied represents an equal-mass binary with spins of equal magnitude
S/m^2=0.43757 \pm 0.00001. The system has initial orbital eccentricity ~4e-5,
and is evolved through 10.6 orbits plus merger and ringdown. The remnant mass
and spin are M_f=(0.961109 \pm 0.000003)M and S_f/M_f^2=0.54781 \pm 0.00001,
respectively, where M is the mass during early inspiral. The gravitational
waveforms have accumulated numerical phase errors of <~ 0.1 radians without any
time or phase shifts, and <~ 0.01 radians when the waveforms are aligned with
suitable time and phase shifts. The waveform is extrapolated to infinity using
a procedure accurate to <~ 0.01 radians in phase, and the extrapolated waveform
differs by up to 0.13 radians in phase and about one percent in amplitude from
the waveform extracted at finite radius r=350M. The simulations employ
different choices for the constraint damping parameters in the wave zone; this
greatly reduces the effects of junk radiation, allowing the extraction of a
clean gravitational wave signal even very early in the simulation.Comment: 14 pages, 15 figure

### A new development cycle of the Statistical Toolkit

The Statistical Toolkit is an open source system specialized in the
statistical comparison of distributions. It addresses requirements common to
different experimental domains, such as simulation validation (e.g. comparison
of experimental and simulated distributions), regression testing in the course
of the software development process, and detector performance monitoring.
Various sets of statistical tests have been added to the existing collection to
deal with the one sample problem (i.e. the comparison of a data distribution to
a function, including tests for normality, categorical analysis and the
estimate of randomness). Improved algorithms and software design contribute to
the robustness of the results. A simple user layer dealing with primitive data
types facilitates the use of the toolkit both in standalone analyses and in
large scale experiments.Comment: To be published in the Proc. of CHEP (Computing in High Energy
Physics) 201

### Approximate initial data for binary black holes

We construct approximate analytical solutions to the constraint equations of
general relativity for binary black holes of arbitrary mass ratio in
quasicircular orbit. We adopt the puncture method to solve the constraint
equations in the transverse-traceless decomposition and consider perturbations
of Schwarzschild black holes caused by boosts and the presence of a binary
companion. A superposition of these two perturbations then yields approximate,
but fully analytic binary black hole initial data that are accurate to first
order in the inverse of the binary separation and the square of the black
holes' momenta.Comment: 13 pages, 4 figures, added comparison to numerical calculations,
accepted to PR

### Crossover and coexistence of quasiparticle excitations in the fractional quantum Hall regime at nu <= 1/3

New low-lying excitations are observed by inelastic light scattering at filling factors nu=p/(phip+/-1) of the fractional quantum Hall regime with phi=4. Coexisting with these modes throughout the range nuless than or equal to1/3 are phi=2 excitations seen at 1/3. Both phi=2 and phi=4 excitations have distinct behaviors with temperature and filling factor. The abrupt first appearance of the new modes in the low-energy excitation spectrum at nuless than or similar to1/3 suggests a marked change in the quantum ground state on crossing the phi=2-->phi=4 boundary at nu=1/3

### Higher gauge theory -- differential versus integral formulation

The term higher gauge theory refers to the generalization of gauge theory to
a theory of connections at two levels, essentially given by 1- and 2-forms. So
far, there have been two approaches to this subject. The differential picture
uses non-Abelian 1- and 2-forms in order to generalize the connection 1-form of
a conventional gauge theory to the next level. The integral picture makes use
of curves and surfaces labeled with elements of non-Abelian groups and
generalizes the formulation of gauge theory in terms of parallel transports. We
recall how to circumvent the classic no-go theorems in order to define
non-Abelian surface ordered products in the integral picture. We then derive
the differential picture from the integral formulation under the assumption
that the curve and surface labels depend smoothly on the position of the curves
and surfaces. We show that some aspects of the no-go theorems are still present
in the differential (but not in the integral) picture. This implies a
substantial structural difference between non-perturbative and perturbative
approaches to higher gauge theory. We finally demonstrate that higher gauge
theory provides a geometrical explanation for the extended topological symmetry
of BF-theory in both pictures.Comment: 26 pages, LaTeX with XYPic diagrams; v2: typos corrected and
presentation improve

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