3,725 research outputs found
Controlling quantum critical dynamics of isolated systems
Controlling the non adiabatic dynamics of isolated quantum systems driven
through a critical point is of interest in a variety of fields ranging from
quantum simulation to finite-time thermodynamics. We briefly review the
different methods for designing protocols which minimize excitation (defect)
production in a closed quantum critical system driven out of equilibrium. We
chart out the role of specific driving schemes for this procedure, point out
their experimental relevance, and discuss their implementation in the context
of ultracold atom and spin systems.Comment: Second version of invited review article submitted to EPJ-ST.
References added, typos corrected. 3 figures, 14 p
Thermal versus quantum fluctuations of optical-lattice fermions
We show that, for fermionic atoms in a one-dimensional optical lattice, the fraction of atoms in doubly occupied sites is a highly nonmonotonic function of temperature. We demonstrate that this property persists even in the presence of realistic harmonic confinement, and that it leads to a suppression of entropy at intermediate temperatures that offers a route to adiabatic cooling. Our interpretation of the suppression is that such intermediate temperatures are simultaneously too high for quantum coherence and too low for significant thermal excitation of double occupancy thus offering a clear indicator of the onset of quantum fluctuations.Publisher PDFPeer reviewe
Inflationary spectra and violations of Bell inequalities
In spite of the macroscopic character of the primordial fluctuations, the
standard inflationary distribution (that obtained using linear mode equations)
exhibits inherently quantum properties, that is, properties which cannot be
mimicked by any stochastic distribution. This is demonstrated by a Gedanken
experiment for which certain Bell inequalities are violated. These violations
are {\it in principle} measurable because, unlike for Hawking radiation from
black holes, in inflationary cosmology we can have access to both members of
correlated pairs of modes delivered in the same state. We then compute the
effect of decoherence and show that the violations persist provided the
decoherence level (and thus the entropy) lies below a certain non-vanishing
threshold. Moreover, there exists a higher threshold above which no violation
of any Bell inequality can occur. In this regime, the distributions are
``separable'' and can be interpreted as stochastic ensembles of fluctuations.
Unfortunately, the precision which is required to have access to the quantum
properties is so high that, {\it in practice}, an observational verification
seems excluded.Comment: 5 pages, 1 figure; new presentation and extended discussio
P02.130. The relationship of client expectations of massage to changes in pain and affect: results from a practice-based research study
Luther-Emery Phase and Atomic-Density Waves in a Trapped Fermion Gas
The Luther-Emery liquid is a state of matter that is predicted to occur in
one-dimensional systems of interacting fermions and is characterized by a
gapless charge spectrum and a gapped spin spectrum. In this Letter we discuss a
realization of the Luther-Emery phase in a trapped cold-atom gas. We study by
means of the density-matrix renormalization-group technique a two-component
atomic Fermi gas with attractive interactions subject to parabolic trapping
inside an optical lattice. We demonstrate how this system exhibits compound
phases characterized by the coexistence of spin pairing and atomic-density
waves. A smooth crossover occurs with increasing magnitude of the atom-atom
attraction to a state in which tightly bound spin-singlet dimers occupy the
center of the trap. The existence of atomic-density waves could be detected in
the elastic contribution to the light-scattering diffraction pattern.Comment: 10 pages, 3 figures, 1 Table, submitted to Phys. Rev. on July 25th
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Exclusive light particle measurements for the system F + C at 96 MeV
Decay sequence of hot {31}^P nucleus has been investigated through
exclusive light charged particle measurements in coincidence with individual
evaporation residues using the reaction {19}^F (96 MeV) + {12}^C.
Information on the sequential decay chain have been extracted by confronting
the data with the predictions of the statistical model. It is observed from the
present analysis that such exclusive light charged particle data may be used as
a powerful tool to probe the decay sequence of the hot light compound systems.Comment: 13 pages, 8 figures, Physical Review C (in press
Beyond Promotion-Based Store Switching:Antecedents and Consequences of Systematic Multiple-Store Shopping
In this paper, we demonstrate that single-purpose multiple store shopping is not only driven by opportunistic, promotion-based motivations, but may also be part of a longer term shopping planning process based on stable store characteristics.Starting from a utility-maximizing shopping behavior model, we find that consumers systematically visit multiple stores to take advantage of two types of store complementarity.With 'fixed cost complementarity', consumers alternate visits to highly preferred but high fixed cost-stores, with in-between trips to less appealing, low fixed cost- stores.This compromise strategy allows them to balance transaction and holding costs against acquisition costs. 'Category preference complementarity' occurs when different stores offer the 'best value' for different product categories.It is found to be an important driver of multiple store shopping, and a necessary condition for combined (chained) shopping trips.Tying these multiple store shopping motivations to characteristics of different grocery store formats leads to interesting new insights into the nature of retail competition and the strategic role of more quality-oriented retail marketing mix instruments.
`Preliminary assays in Red Snapper Lutjanus synagris (Linnaeus, 1758) semen cryopreservation through the application of Dimethyl-Sulfoxide (DMSO) and 1,2 Propadiol Cryoprotectors with Santa Marta’s (Colombia) biological material [Poster abstract]
Friedel oscillations in one-dimensional metals: from Luttinger's theorem to the Luttinger liquid
Charge density and magnetization density profiles of one-dimensional metals
are investigated by two complementary many-body methods: numerically exact
(Lanczos) diagonalization, and the Bethe-Ansatz local-density approximation
with and without a simple self-interaction correction. Depending on the
magnetization of the system, local approximations reproduce different Fourier
components of the exact Friedel oscillations.Comment: 3 pages, 3 figures, Manuscript accepted by Journal of Magnetism and
Magnetic Materials, special issue for LAWMMM 2007 conferenc
Shortcuts to adiabaticity in a time-dependent box
A method is proposed to drive an ultrafast non-adiabatic dynamics of an
ultracold gas trapped in a box potential. The resulting state is free from
spurious excitations associated with the breakdown of adiabaticity, and
preserves the quantum correlations of the initial state up to a scaling factor.
The process relies on the existence of an adiabatic invariant and the inversion
of the dynamical self-similar scaling law dictated by it. Its physical
implementation generally requires the use of an auxiliary expulsive potential
analogous to those used in soliton control. The method is extended to a broad
family of many-body systems. As illustrative examples we consider the ultrafast
expansion of a Tonks-Girardeau gas and of Bose-Einstein condensates in
different dimensions, where the method exhibits an excellent robustness against
different regimes of interactions and the features of an experimentally
realizable box potential.Comment: 6 pp, 4 figures, typo in Eq. (6) fixe
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