1,305 research outputs found
Entanglement and the Born-Oppenheimer approximation in an exactly solvable quantum many-body system
We investigate the correlations between different bipartitions of an exactly
solvable one-dimensional many-body Moshinsky model consisting of Nn "nuclei"
and Ne "electrons". We study the dependence of entanglement on the
inter-particle interaction strength, on the number of particles, and on the
particle masses. Consistent with kinematic intuition, the entanglement between
two subsystems vanishes when the subsystems have very different masses, while
it attains its maximal value for subsystems of comparable mass. We show how
this entanglement feature can be inferred by means of the Born-Oppenheimer
Ansatz, whose validity and breakdown can be understood from a quantum
information point of view.Comment: Accepted in Eur. Phys. J. D (2014
Bosonic behavior of entangled fermions
Two bound, entangled fermions form a composite boson, which can be treated as
an elementary boson as long as the Pauli principle does not affect the behavior
of many such composite bosons. The departure of ideal bosonic behavior is
quantified by the normalization ratio of multi-composite-boson states. We
derive the two-fermion-states that extremize the normalization ratio for a
fixed single-fermion purity P, and establish general tight bounds for this
indicator. For very small purities, P<1/N^2, the upper and lower bounds
converge, which allows to quantify accurately the departure from perfectly
bosonic behavior, for any state of many composite bosons.Comment: 9 pages, 5 figures, accepted by PR
Binary black holes on a budget: Simulations using workstations
Binary black hole simulations have traditionally been computationally very
expensive: current simulations are performed in supercomputers involving dozens
if not hundreds of processors, thus systematic studies of the parameter space
of binary black hole encounters still seem prohibitive with current technology.
Here we show how the multi-layered refinement level code BAM can be used on
dual processor workstations to simulate certain binary black hole systems. BAM,
based on the moving punctures method, provides grid structures composed of
boxes of increasing resolution near the center of the grid. In the case of
binaries, the highest resolution boxes are placed around each black hole and
they track them in their orbits until the final merger when a single set of
levels surrounds the black hole remnant. This is particularly useful when
simulating spinning black holes since the gravitational fields gradients are
larger. We present simulations of binaries with equal mass black holes with
spins parallel to the binary axis and intrinsic magnitude of S/m^2= 0.75. Our
results compare favorably to those of previous simulations of this particular
system. We show that the moving punctures method produces stable simulations at
maximum spatial resolutions up to M/160 and for durations of up to the
equivalent of 20 orbital periods.Comment: 20 pages, 8 figures. Final version, to appear in a special issue of
Class. Quantum Grav. based on the New Frontiers in Numerical Relativity
Conference, Golm, July 200
20th Workshop on Automotive Software Engineering (ASE’23)
Software-based systems play an increasingly important role and enable most innovations in modern cars. This workshop will address various topics related to automotive software development. The participants will discuss appropriate methods, techniques, and tools needed to address the most current challenges for researchers and practitioners
Quasi-equilibrium binary black hole sequences for puncture data derived from helical Killing vector conditions
We construct a sequence of binary black hole puncture data derived under the
assumptions (i) that the ADM mass of each puncture as measured in the
asymptotically flat space at the puncture stays constant along the sequence,
and (ii) that the orbits along the sequence are quasi-circular in the sense
that several necessary conditions for the existence of a helical Killing vector
are satisfied. These conditions are equality of ADM and Komar mass at infinity
and equality of the ADM and a rescaled Komar mass at each puncture. In this
paper we explicitly give results for the case of an equal mass black hole
binary without spin, but our approach can also be applied in the general case.
We find that up to numerical accuracy the apparent horizon mass also remains
constant along the sequence and that the prediction for the innermost stable
circular orbit is similar to what has been found with the effective potential
method.Comment: 6 pages, 3 figures, 1 tabl
Hands-On Russian Culture Lessons
The global diverse society necessitates that teachers develop cultural competency and use authentic resources for teaching. This article presents classroom-tested materials for teaching elementary students about aspects of Russian culture, developed by a native Russian and two education professors. Multiage, multi-racial American Midwestern students from a homeschooling cooperative learned vocabulary and concepts with statistically significant increases from pretest to posttest and a large effect size. The lessons began with recognition of human commonalities between Russian people and Americans, in accordance with omniculturalism theory. Lessons then highlighted and celebrated cultural differences through an exploration of Russian literature and culture. Culminating creative craft-making activities included simulating a Gzhel porcelain statue in white air-dry clay with blue markings, making a pop-up version of a matryoshka nesting doll set, constructing a papier-maché building with onion-domed towers and a Maslenitsa holiday scene, and decorating a paper-covered plastic egg with gems to make a Faberge-style jewelry box. The lessons, greeted with enthusiasm from students, included classification tasks, observation activities, and a Bingo-type game. Students evidenced deeper learning by continuing to connect their lives to Russian cultural content after the lesson unit had concluded
Impurity Effects in Two-Electron Coupled Quantum Dots: Entanglement Modulation
We present a detailed analysis of the electronic and optical properties of
two-electron quantum dots with a two-dimensional Gaussian confinement
potential. We study the effects of Coulomb impurities and the possibility of
manipulate the entanglement of the electrons by controlling the confinement
potential parameters. The degree of entanglement becomes highly modulated by
both the location and charge screening of the impurity atom, resulting two
regimes: one of low entanglement and other of high entanglement, with both of
them mainly determined by the magnitude of the charge. It is shown that the
magnitude of the oscillator strength of the system could provide an indication
of the presence and characteristics of impurities that could largely influence
the degree of entanglement of the system.Comment: Regular Article (Journal of Physics B, in press), 9 pages, 10 figure
Initial data for binary neutron stars with arbitrary spins
In general neutron stars in binaries are spinning. Due to the existence of
millisecond pulsars we know that these spins can be substantial. We argue that
spins with periods on the order a few dozen milliseconds could influence the
late inspiral and merger dynamics. Thus numerical simulations of the last few
orbits and the merger should start from initial conditions that allow for
arbitrary spins. We discuss quasi-equilibrium approximations one can make in
the construction of binary neutron star initial data with spins. Using these
approximations we are able to derive two new matter equations. As in the case
of irrotational neutron star binaries one of these equations is algebraic and
the other elliptic. If these new matter equations are solved together with the
equations for the metric variables following the Wilson-Mathews or conformal
thin sandwich approach one can construct neutron star initial data. The spin of
each star is described by a rotational velocity that can be chosen freely so
that one can create stars in arbitrary rotation states. Our new matter
equations reduce to the well known limits of both corotating and irrotational
neutron star binaries.Comment: 9 page
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