14,010 research outputs found
Scale invariant thermodynamics of a toroidally trapped Bose gas
We consider a system of bosonic atoms in an axially symmetric harmonic trap
augmented with a two dimensional repulsive Gaussian optical potential. We find
an expression for the grand free energy of the system for configurations
ranging from the harmonic trap to the toroidal regime. For large tori we
identify an accessible regime where the ideal gas thermodynamics of the system
are found to be independent of toroidal radius. This property is a consequence
of an invariant extensive volume of the system that we identify analytically in
the regime where the toroidal potential is radially harmonic. In considering
corrections to the scale invariant transition temperature, we find that the
first order interaction shift is the dominant effect in the thermodynamic
limit, and is also scale invariant. We also consider adiabatic loading from the
harmonic to toroidal trap configuration, which we show to have only a small
effect on the condensate fraction of the ideal gas, indicating that loading
into the scale invariant regime may be experimentally practical.Comment: 10 pages, 3 figures, to appear in Phys. Rev. A, typos corrected,
references added, rewritten to emphasize generalized volume. Results
unchange
Probing Phases and Quantum Criticality using Deviations from the Local Fluctuation-Dissipation Theorem
Introduction Cold atomic gases in optical lattices are emerging as excellent
laboratories for testing models of strongly interacting particles in condensed
matter physics. Currently, one of the major open questions is how to obtain the
finite temperature phase diagram of a given quantum Hamiltonian directly from
experiments. Previous work in this direction required quantum Monte Carlo
simulations to directly model the experimental situation in order to extract
quantitative information, clearly defeating the purpose of an optical lattice
emulator. Here we propose a new method that utilizes deviations from a local
fluctuation dissipation theorem to construct a finite temperature phase
diagram, for the first time, from local observables accessible by in situ
experimental observations. Our approach extends the utility of the
fluctuation-dissipation theorem from thermometry to the identification of
quantum phases, associated energy scales and the quantum critical region. We
test our ideas using state-of-the-art large-scale quantum Monte Carlo
simulations of the two-dimensional Bose Hubbard model.Comment: 7 pages; 4 figures; also see supplementary material of 7 pages with 3
figure
On Flux Quantization in F-Theory II: Unitary and Symplectic Gauge Groups
We study the quantization of the M-theory G-flux on elliptically fibered
Calabi-Yau fourfolds with singularities giving rise to unitary and symplectic
gauge groups. We seek and find its relation to the Freed-Witten quantization of
worldvolume fluxes on 7-branes in type IIB orientifold compactifications on
Calabi-Yau threefolds. By explicitly constructing the appropriate four-cycles
on which to calculate the periods of the second Chern class of the fourfolds,
we find that there is a half-integral shift in the quantization of G-flux
whenever the corresponding dual 7-brane is wrapped on a non-spin submanifold.
This correspondence of quantizations holds for all unitary and symplectic gauge
groups, except for SU(3), which behaves mysteriously. We also perform our
analysis in the case where, in addition to the aforementioned gauge groups,
there is also a 'flavor' U(1)-gauge group.Comment: 33 pages, 4 figure
A VON LIEBIG MODEL FOR WATER AND NITROGEN CROP RESPONSE
The century-old “law of the minimum” proposed by von Liebig was tested using five independent sets of crop response data on wheat, corn, cotton, silage, and sugar beets. The rival models were polynomial functions reported in the literature as the most suitable models for interpreting those data. Overall, the von Liebig model performed very well. While the nonnested hypothesis test was inconclusive with regard to silage and sugar beets, the von Liebig model rejected the polynomial specifications for wheat, corn and cotton.Crop Production/Industries,
Interpretation of the northern boundary of Ishtar Terra from Magellan images and altimetry
Part of the controversy on the origin of western Ishtar Terra (IT) concerns the nature of Uorsar Rupes (UR), the northern boundary of IT. In the hypothesis of lithospheric convergence and underthrusting, UR is held to be the main boundary thrust fault at the toe of an accretionary wedge. A topographic rise parallel to the scarp was interpreted as a flexural bulge similar to those of terrestrial subduction zones, and quantitative models of this feature seemed broadly consistent with the expected lithospheric structure of Venus. In the alternative mantle upwelling hypothesis for western IT, the outer margins of the highland are thought to be collapsing, and UR has been interpreted as a normal fault. Herein, Magellan images and altimetry are interpreted for this region and the hypothesis that a flexural signature can be distinguished is reassessed. The Magellan images of IT show evidence of crustal shortening adjacent to UR, but extension and burial dominate northwards. Altimetric profiles display the same long wavelength trends visible in Venera data, but no clear evidence of the lithospheric flexure. A model of regional extension and burial is herein favored, but regional compression cannot be ruled out
Solvable RSOS models based on the dilute BWM algebra
In this paper we present representations of the recently introduced dilute
Birman-Wenzl-Murakami algebra. These representations, labelled by the level-
B, C and D affine Lie algebras, are Baxterized to
yield solutions to the Yang-Baxter equation.
The thus obtained critical solvable models are RSOS counterparts of the,
respectively, D, and B -matrices of
Bazhanov and Jimbo. For the D and B algebras the RSOS
models are new. An elliptic extension which solves the Yang-Baxter equation is
given for all three series of dilute RSOS models.Comment: 25 pages, uuencoded compressed PostScript file, Amsterdam preprint
ITFA-94-2
The SEALS Yardsticks for Ontology Management
This paper describes the rst SEALS evaluation campaign
over ontology engineering tools (i.e., the SEALS Yardsticks for Ontology Management). It presents the dierent evaluation scenarios dened to evaluate the conformance, interoperability and scalability of these tools, and the test data used in these scenarios
How Do Quasicrystals Grow?
Using molecular simulations, we show that the aperiodic growth of
quasicrystals is controlled by the ability of the growing quasicrystal
`nucleus' to incorporate kinetically trapped atoms into the solid phase with
minimal rearrangement. In the system under investigation, which forms a
dodecagonal quasicrystal, we show that this process occurs through the
assimilation of stable icosahedral clusters by the growing quasicrystal. Our
results demonstrate how local atomic interactions give rise to the long-range
aperiodicity of quasicrystals.Comment: 4 pages, 4 figures. Figures and text have been updated to the final
version of the articl
Observation of the Pairing Gap in a Strongly Interacting Fermi Gas
We study fermionic pairing in an ultracold two-component gas of Li atoms
by observing an energy gap in the radio-frequency excitation spectra. With
control of the two-body interactions via a Feshbach resonance we demonstrate
the dependence of the pairing gap on coupling strength, temperature, and Fermi
energy. The appearance of an energy gap with moderate evaporative cooling
suggests that our full evaporation brings the strongly interacting system deep
into a superfluid state.Comment: 18 pages, 3 figure
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