8,026 research outputs found
Gravitational Waves from Wobbling Pulsars
The prospects for detection of gravitational waves from precessing pulsars
have been considered by constructing fully relativistic rotating neutron star
models and evaluating the expected wave amplitude from a galactic source.
For a "typical" neutron matter equation of state and observed rotation rates,
it is shown that moderate wobble angles may render an observable signal from a
nearby source once the present generation of interferometric antennas becomes
operative.Comment: PlainTex, 7 pp. , no figures, IAG/USP Rep. 6
Statistical stability and limit laws for Rovella maps
We consider the family of one-dimensional maps arising from the contracting
Lorenz attractors studied by Rovella. Benedicks-Carleson techniques were used
by Rovella to prove that there is a one-parameter family of maps whose
derivatives along their critical orbits increase exponentially fast and the
critical orbits have slow recurrent to the critical point. Metzger proved that
these maps have a unique absolutely continuous ergodic invariant probability
measure (SRB measure).
Here we use the technique developed by Freitas and show that the tail set
(the set of points which at a given time have not achieved either the
exponential growth of derivative or the slow recurrence) decays exponentially
fast as time passes. As a consequence, we obtain the continuous variation of
the densities of the SRB measures and associated metric entropies with the
parameter. Our main result also implies some statistical properties for these
maps.Comment: 1 figur
Statistical stability of equilibrium states for interval maps
We consider families of multimodal interval maps with polynomial growth of
the derivative along the critical orbits. For these maps Bruin and Todd have
shown the existence and uniqueness of equilibrium states for the potential
, for close to 1. We show that these
equilibrium states vary continuously in the weak topology within such
families. Moreover, in the case , when the equilibrium states are
absolutely continuous with respect to Lebesgue, we show that the densities vary
continuously within these families.Comment: More details given and the appendices now incorporated into the rest
of the pape
Strong evidences for a nonextensive behavior of the rotation period in Open Clusters
Time-dependent nonextensivity in a stellar astrophysical scenario combines
nonextensive entropic indices derived from the modified Kawaler's
parametrization, and , obtained from rotational velocity distribution. These
's are related through a heuristic single relation given by , where is the cluster age. In a nonextensive
scenario, these indices are quantities that measure the degree of
nonextensivity present in the system. Recent studies reveal that the index
is correlated to the formation rate of high-energy tails present in the
distribution of rotation velocity. On the other hand, the index is
determined by the stellar rotation-age relationship. This depends on the
magnetic field configuration through the expression , where
and denote the saturation level of the star magnetic field and its
topology, respectively. In the present study, we show that the connection
is also consistent with 548 rotation period data for single
main-sequence stars in 11 Open Clusters aged less than 1 Gyr. The value of
2.5 from our unsaturated model shows that the mean magnetic field
topology of these stars is slightly more complex than a purely radial field.
Our results also suggest that stellar rotational braking behavior affects the
degree of anti-correlation between and cluster age . Finally, we suggest
that stellar magnetic braking can be scaled by the entropic index .Comment: 6 pages and 2 figures, accepted to EPL on October 17, 201
The parameter at three loops and elliptic integrals
We describe the analytic calculation of the master integrals required to
compute the two-mass three-loop corrections to the parameter. In
particular, we present the calculation of the master integrals for which the
corresponding differential equations do not factorize to first order. The
homogeneous solutions to these differential equations are obtained in terms of
hypergeometric functions at rational argument. These hypergeometric functions
can further be mapped to complete elliptic integrals, and the inhomogeneous
solutions are expressed in terms of a new class of integrals of combined
iterative non-iterative nature.Comment: 14 pages Latex, 7 figures, to appear in the Proceedings of "Loops and
Legs in Quantum Field Theory - LL 2018", 29 April - 4 May 2018, Po
3-loop Massive Contributions to the DIS Operator Matrix Element
Contributions to heavy flavour transition matrix elements in the variable
flavour number scheme are considered at 3-loop order. In particular a
calculation of the diagrams with two equal masses that contribute to the
massive operator matrix element is performed. In the Mellin
space result one finds finite nested binomial sums. In -space these sums
correspond to iterated integrals over an alphabet containing also square-root
valued letters.Comment: 4 pages, Contribution to the Proceedings of QCD '14, Montpellier,
July 201
A nonextensive insight to the stellar initial mass function
the present paper, we propose that the stellar initial mass distributions as
known as IMF are best fitted by -Weibulls that emerge within nonextensive
statistical mechanics. As a result, we show that the Salpeter's slope of
2.35 is replaced when a -Weibull distribution is used. Our results
point out that the nonextensive entropic index represents a new approach
for understanding the process of the star-forming and evolution of massive
stars.Comment: 5 pages, 2 figures, Accepted to EP
3-Loop Heavy Flavor Corrections in Deep-Inelastic Scattering with Two Heavy Quark Lines
We consider gluonic contributions to the heavy flavor Wilson coefficients at
3-loop order in QCD with two heavy quark lines in the asymptotic region . Here we report on the complete result in the case of two equal
masses for the massive operator matrix element ,
which contributes to the corresponding heavy flavor transition matrix element
in the variable flavor number scheme. Nested finite binomial sums and iterated
integrals over square-root valued alphabets emerge in the result for this
quantity in and -space, respectively. We also present results for the
case of two unequal masses for the flavor non-singlet OMEs and on the scalar
integrals ic case of , which were calculated without a further
approximation. The graphs can be expressed by finite nested binomial sums over
generalized harmonic sums, the alphabet of which contains rational letters in
the ratio .Comment: 10 pages LATEX, 1 Figure, Proceedings of Loops and Legs in Quantum
Field Theory, Weimar April 201
The Distance to the M31 Globular Cluster System
The distance to the centroid of the M31 globular cluster system is determined
by fitting theoretical isochrones to the observed red-giant branches of
fourteen globular clusters in M31. The mean true distance modulus of the M31
globular clusters is found to be 24.47 +/- 0.07 mag. This is consistent with
distance modulii for M31 that have been obtained using other distance
indicators.Comment: 11 pages, 2 postscript figures, uses aaspp4.sty, to be published in
the May 1998 Astronomical Journa
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