25,955 research outputs found
Comment on "General Non-Markovian Dynamics of Open Quantum Systems"
The existence of a "non-Markovian dissipationless" regime, characterized by
long lived oscillations, was recently reported for a class of quantum open
systems (Zhang et al, PRL, 109, 170402, (2012)). It is claimed this could
happen in the strong coupling regime, a surprising result which has attracted
some attention. We show that this regime exists if and only if the total
Hamiltonian is unbounded from below, casting serious doubts on the usefulness
of this result
Generation of bipartite spin entanglement via spin-independent scattering
We consider the bipartite spin entanglement between two identical fermions
generated in spin-independent scattering. We show how the spatial degrees of
freedom act as ancillas for the creation of entanglement to a degree that
depends on the scattering angle, . The number of Slater determinants
generated in the process is greater than 1, corresponding to genuine quantum
correlations between the identical fermions. The maximal entanglement
attainable of 1 ebit is reached at . We also analyze a simple
dependent Bell's inequality, which is violated for
. This phenomenon is unrelated to the symmetrization
postulate but does not appear for unequal particles.Comment: 5 pages and 3 figures. Accepted in PR
Defning a core genome for the Herpesvirales and exploring their evolutionary relationship with the Caudovirales
Plio-Pleistocene time-averaged field in southern Patagonia recorded in lava flows
Paleomagnetic directions were obtained from stepwise alternating-field or thermal demagnetization of 53 lava flows from southern Patagonia (latitudes 49.5°-52.1 °S) that include the Pali-Aike volcanic field and the Meseta Viscachas plateau lavas. In addition to previous Miocene-late Quaternary ages of these flows, 40Ar/39Ar dates spanning from 0.1 to 15.4 Ma were obtained for 17 of the sites. All except one of the magnetic polarities coincide with the expected polarities of the magnetic polarity timescale [Cande and Kent, 1995] for the obtained 40Ar/39Ar ages. The mean direction from 33 sites (eliminating sites <4 Ma) that pass a selection criteria of α95 ≤5° is Dec = 358.7°,Inc = - 68.2°, α95 = 3.5°, a value that coincides within the statistical uncertainty with the direction of the geocentric axial dipole for that area (Inc = - 68.1°). Likewise, the mean virtual geomagnetic pole (VGP) coincides within the statistical uncertainty with the geographic North Pole. The secular variation described by the VGP angular standard deviation for these sites is 17.1°, a value expected for that latitude according to Model G of paleosecular variation [McFadden et al., 1988]. The characteristics of the data presented are optimum for time-averaged field (TAF) studies because of the good age control and good quality of the paleomagnetic data: (1) primary components of magnetization were obtained using principal component analysis [Kirschvink, 1980] from at least five points and maximum angular deviation ≤5°, (2) site means were calculated with Fisher statistics using at least three samples, and (c) 38 of the 53 flows had α95 ≤ 5°. No results (five sites) or high α95 values (≤5°) were obtained primarily from sites affected by lightning.Fil: Mejia, V.. University of Florida; Estados UnidosFil: Opdyke, N. D.. University of Florida; Estados UnidosFil: Vilas, Juan Francisco A.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de GeologÃa; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Singer, B. S.. University of Wisconsin; Estados UnidosFil: Stoner, J. S.. State University of Colorado at Boulder; Estados Unido
The Kepler problem and non commutativity
We investigate the Kepler problem using a symplectic structure consistent
with the commutation rules of the noncommutative quantum mechanics. We show
that a noncommutative parameter of the order of gives
observable corrections to the movement of the solar system. In this way,
modifications in the physics of smaller scales implies modifications at large
scales, something similar to the UV/IR mixing.Comment: 10 page
Time relaxation of interacting single--molecule magnets
We study the relaxation of interacting single--molecule magnets (SMMs) in
both spatially ordered and disordered systems. The tunneling window is assumed
to be, as in Fe8, much narrower than the dipolar field spread. We show that
relaxation in disordered systems differs qualitatively from relaxation in fully
occupied cubic and Fe_8 lattices. We also study how line shapes that develop in
''hole--digging'' experiments evolve with time t in these fully occupied
lattices. We show (1) that the dipolar field h scales as t^p in these hole line
shapes and show (2) how p varies with lattice structure. Line shapes are not,
in general, Lorentzian. More specifically, in the lower portion of the hole,
they behave as (h/t^p)^{(1/p)-1} if h is outside the tunnel window. This is in
agreement with experiment and with our own Monte Carlo results.Comment: 21 LaTeX pages, 6 eps figures. Submitted to PRB on 15 June 2005.
Accepted on 13 August 200
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