7,794 research outputs found
Reducing the weak lensing noise for the gravitational wave Hubble diagram using the non-Gaussianity of the magnification distribution
Gravitational wave sources are a promising cosmological standard candle
because their intrinsic luminosities are determined by fundamental physics (and
are insensitive to dust extinction). They are, however, affected by weak
lensing magnification due to the gravitational lensing from structures along
the line of sight. This lensing is a source of uncertainty in the distance
determination, even in the limit of perfect standard candle measurements. It is
commonly believed that the uncertainty in the distance to an ensemble of
gravitational wave sources is limited by the standard deviation of the lensing
magnification distribution divided by the square root of the number of sources.
Here we show that by exploiting the non-Gaussian nature of the lensing
magnification distribution, we can improve this distance determination,
typically by a factor of 2--3; we provide a fitting formula for the effective
distance accuracy as a function of redshift for sources where the lensing noise
dominates.Comment: matches PRD accepted version (expanded description of the
cosmological parameter space + minor changes
Phase coexistence in proton glass
Proton glasses are crystals of composition M{sub 1{minus}x}(NW{sub 4}){sub x}W{sub 2}AO{sub 4}, where M = K,Rb, W = H,D, A = P,As. For x = 0 there is a ferroelectric (FE) transition, while for x = 1 there is an antiferroelectric (AFE) transition. In both cases, the transition is from a paraelectric (PE) state of tetragonal structure with dynamically disordered hydrogen bonds to an ordered state of orthorhombic structure. For an intermediate x range there is no transition, but the hydrogen rearrangements slow down, and eventually display nonergodic behavior characteristic of glasses. The authors and other have shown from spontaneous polarization, dielectric permittivity, nuclear magnetic resonance, and neutron diffraction experiments that for smaller x there is coexistence of ferroelectric and paraelectric phases, and for larger x there is coexistence of antiferroelectric and paraelectric phases. The authors present a method for analytically describing this coexistence, and the degree to which this coexistence is spatial or temporal
Spatial field correlation, the building block of mesoscopic fluctuations
The absence of self averaging in mesoscopic systems is a consequence of
long-range intensity correlation. Microwave measurements suggest and
diagrammatic calculations confirm that the correlation function of the
normalized intensity with displacement of the source and detector,
and , respectively, can be expressed as the sum of three terms, with
distinctive spatial dependences. Each term involves only the sum or the product
of the square of the field correlation function, . The
leading-order term is the product, the next term is proportional to the sum.
The third term is proportional to .Comment: Submitted to PR
Field-induced 3- and 2-dimensional freezing in a quantum spin liquid
Field-induced commensurate transverse magnetic ordering is observed in the
Haldane-gap compound \nd by means of neutron diffraction. Depending on the
direction of applied field, the high-field phase is shown to be either a
3-dimensional ordered N\'{e}el state or a short-range ordered state with
dominant 2-dimensional spin correlations. The structure of the high-field phase
is determined, and properties of the observed quantum phase transition are
discussed.Comment: 4 pages 3 figure
Equatorial circular orbits in the Kerr-de Sitter spacetimes
Equatorial motion of test particles in the Kerr-de Sitter spacetimes is
considered. Circular orbits are determined, their properties are discussed for
both the black-hole and naked-singularity spacetimes, and their relevance for
thin accretion discs is established.Comment: 24 pages, 19 figures, REVTeX
An Optimal Algorithm for Tiling the Plane with a Translated Polyomino
We give a -time algorithm for determining whether translations of a
polyomino with edges can tile the plane. The algorithm is also a
-time algorithm for enumerating all such tilings that are also regular,
and we prove that at most such tilings exist.Comment: In proceedings of ISAAC 201
A holomorphic representation of the Jacobi algebra
A representation of the Jacobi algebra by first order differential operators with polynomial
coefficients on the manifold is presented. The
Hilbert space of holomorphic functions on which the holomorphic first order
differential operators with polynomials coefficients act is constructed.Comment: 34 pages, corrected typos in accord with the printed version and the
Errata in Rev. Math. Phys. Vol. 24, No. 10 (2012) 1292001 (2 pages) DOI:
10.1142/S0129055X12920018, references update
Anomalous phonon behavior in the high temperature shape memory alloy: TiPd:Cr
Ti50 Pd50-xCrx is a high temperature shape memory alloy with a martensitic
transformation temperature strongly dependent on the Cr composition. Prior to
the transformation a premartensitic phase is present with an incommensurate
modulated cubic lattice with wave vector of q0=(0.22, 0.22, 0). The temperature
dependence of the diffuse scattering in the cubic phase is measured as a
function temperature for x=6.5, 8.5, and 10 at. %. The lattice dynamics has
been studied and reveals anomalous temperature and q-dependence of the
[110]-TA2 transverse phonon branch. The phonon linewidth is broad over the
entire Brillouin zone and increases with decreasing temperature, contrary to
the behavior expected for anharmonicity. No anomaly is observed at q0. The
results are compared with first principles calculation of the phonon structure.Comment: 26 pages, 11 figure
Black-Hole Spin Dependence in the Light Curves of Tidal Disruption Events
A star orbiting a supermassive black hole can be tidally disrupted if the
black hole's gravitational tidal field exceeds the star's self gravity at
pericenter. Some of this stellar tidal debris can become gravitationally bound
to the black hole, leading to a bright electromagnetic flare with bolometric
luminosity proportional to the rate at which material falls back to pericenter.
In the Newtonian limit, this flare will have a light curve that scales as
t^-5/3 if the tidal debris has a flat distribution in binding energy. We
investigate the time dependence of the black-hole mass accretion rate when
tidal disruption occurs close enough the black hole that relativistic effects
are significant. We find that for orbits with pericenters comparable to the
radius of the marginally bound circular orbit, relativistic effects can double
the peak accretion rate and halve the time it takes to reach this peak
accretion rate. The accretion rate depends on both the magnitude of the
black-hole spin and its orientation with respect to the stellar orbit; for
orbits with a given pericenter radius in Boyer-Lindquist coordinates, a maximal
black-hole spin anti-aligned with the orbital angular momentum leads to the
largest peak accretion rate.Comment: 16 pages, 15 figures, 1 table, PRD published versio
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