3,938 research outputs found
Jump-diffusion unravelling of a non Markovian generalized Lindblad master equation
The "correlated-projection technique" has been successfully applied to derive
a large class of highly non Markovian dynamics, the so called non Markovian
generalized Lindblad type equations or Lindblad rate equations. In this
article, general unravellings are presented for these equations, described in
terms of jump-diffusion stochastic differential equations for wave functions.
We show also that the proposed unravelling can be interpreted in terms of
measurements continuous in time, but with some conceptual restrictions. The
main point in the measurement interpretation is that the structure itself of
the underlying mathematical theory poses restrictions on what can be considered
as observable and what is not; such restrictions can be seen as the effect of
some kind of superselection rule. Finally, we develop a concrete example and we
discuss possible effects on the heterodyne spectrum of a two-level system due
to a structured thermal-like bath with memory.Comment: 23 page
Spectroscopic determination of the s-wave scattering lengths of 86Sr and 88Sr
We report the use of photoassociative spectroscopy to determine the ground
state s-wave scattering lengths for the main bosonic isotopes of strontium,
86Sr and 88Sr. Photoassociative transitions are driven with a laser red-detuned
by up to 1400 GHz from the 1S0-1P1 atomic resonance at 461 nm. A minimum in the
transition amplitude for 86Sr at -494+/-5 GHz allows us to determine the
scattering lengths 610a0 < a86 < 2300a0 for 86Sr and a much smaller value of
-1a0 < a88 < 13a0 for 88Sr.Comment: 4 pages, 3 figures, submitted to Physical Review Letter
The survival and destruction of X-ray coronae of early-type galaxies in the rich cluster environments: a case study of Abell 1367
A new Chandra observation of the northwest region of the galaxy cluster A1367
reveals four cool galaxy coronae (0.4 - 1.0 keV) embedded in the hot
intracluster medium (ICM) (5 - 6 keV). While the large coronae of NGC 3842 and
NGC 3837 appear symmetric and relaxed, the galaxy coronae of the \lsim L*
galaxies (NGC 3841 and CGCG 97090) are disturbed and being stripped. Massive
galaxies, with dense cooling cores, are better able to resist ram pressure
stripping and survive in rich environments than \lsim L* galaxies whose
galactic coronae are much less dense. The survival of these cool coronae
implies that thermal conduction from the hot surrounding ICM has to be
suppressed by a factor of at least 60, at the corona boundary. Within the
galaxy coronae of NGC 3842 and NGC 3837, stellar mass loss or heat conduction
with the Spitzer value may be sufficient to balance radiative cooling. Energy
deposition at the ends of collimated jets may heat the outer coronae, but allow
the survival of a small, dense gas core (e.g., NGC 3842 in A1367 and NGC 4874
in Coma). The survived X-ray coronae become significantly smaller and fainter
with the increasing ambient pressure.Comment: 11 pages, 7 figures, emulateapj5, accepted by Ap
Redshift-Distance Survey of Early-Type Galaxies. IV. Dipoles of the Velocity Field
We use the recently completed redshift-distance survey of nearby early-type
galaxies (ENEAR) to measure the dipole component of the peculiar velocity field
to a depth of cz ~ 6000 km/s. The sample consists of 1145 galaxies brighter
than m_B=14.5 and cz < 7000 km/s, uniformly distributed over the whole sky, and
129 fainter cluster galaxies within the same volume. Most of the Dn-sigma
distances were obtained from new spectroscopic and photometric observations
conducted by this project, ensuring the homogeneity of the data over the whole
sky. These 1274 galaxies are objectively assigned to 696 objects -- 282
groups/clusters and 414 isolated galaxies. We find that within a volume of
radius ~ 6000 km/s, the best-fitting bulk flow has an amplitude of |vbulk| =220
+/- 42 km/s in the CMB restframe, pointing towards l=304 +/- 16 degrees, b=25
+/- 11 degrees. The error in the amplitude includes statistical, sampling and
possible systematic errors. This solution is in excellent agreement with that
obtained by the SFI Tully-Fisher survey. Our results suggest that most of the
motion of the Local Group is due to fluctuations within 6000 km/s, in contrast
to recent claims of large amplitude bulk motions on larger scales.Comment: 11 pages, 2 figures, ApJL, accepted (updated results; matches
accepted version
Path Integral Approach to Strongly Nonlinear Composite
We study strongly nonlinear disordered media using a functional method. We
solve exactly the problem of a nonlinear impurity in a linear host and we
obtain a Bruggeman-like formula for the effective nonlinear susceptibility.
This formula reduces to the usual Bruggeman effective medium approximation in
the linear case and has the following features: (i) It reproduces the weak
contrast expansion to the second order and (ii) the effective medium exponent
near the percolation threshold are , , where is the
nonlinearity exponent. Finally, we give analytical expressions for previously
numerically calculated quantities.Comment: 4 pages, 1 figure, to appear in Phys. Rev.
Nuclear Cusps and Cores in Early-type Galaxies As Relics of Binary Black Hole Mergers
We present an analysis of the central cusp slopes and core parameters of
early-type galaxies using a large database of surface brightness profiles
obtained from Hubble Space Telescope observations. We examine the relation
between the central cusp slopes, core parameters, and black hole masses in
early-type galaxies, in light of two models that attempt to explain the
formation of cores and density cusps via the dynamical influence of black
holes. Contrary to the expectations from adiabatic-growth models, we find that
the cusp slopes do not steepen with increasing black hole mass fraction.
Moreover, a comparison of kinematic black hole mass measurements with the
masses predicted by the adiabatic models shows that they overpredict the masses
by a factor of approximately 3. Simulations involving binary black hole mergers
predict that both the size of the core and the central mass deficit correlate
with the final black hole mass. These relations are qualitatively supported by
the present data.Comment: To appear in ApJ. 8 page
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