719 research outputs found
Atomic quantum gases in Kagom\'e lattices
We demonstrate the possibility of creating and controlling an ideal and
\textit{trimerized} optical Kagom\'e lattice, and study the low temperature
physics of various atomic gases in such lattices. In the trimerized Kagom\'e
lattice, a Bose gas exhibits a Mott transition with fractional filling factors,
whereas a spinless interacting Fermi gas at 2/3 filling behaves as a quantum
magnet on a triangular lattice. Finally, a Fermi-Fermi mixture at half filling
for both components represents a frustrated quantum antiferromagnet with a
resonating-valence-bond ground state and quantum spin liquid behavior dominated
by continuous spectrum of singlet and triplet excitations. We discuss the
method of preparing and observing such quantum spin liquid employing molecular
Bose condensates.Comment: 4 pages, 1 figure. Missing affiliations adde
Hierarchical approach to matched filtering using a reduced basis
Searching for gravitational waves from compact binary coalescences (CBC) is performed by matched filtering the observed strain data from gravitational-wave observatories against a discrete set of waveform templates designed to accurately approximate the expected gravitational-wave signal, and are chosen to efficiently cover a target search region. The computational cost of matched filtering scales with both the number of templates required to cover a parameter space and the in-band duration of the waveform. Both of these factors increase in difficulty as the current observatories improve in sensitivity, especially at low frequencies, and may pose challenges for third-generation observatories. Reducing the cost of matched filtering would make searches of future detector's data more tractable. In addition, it would be easier to conduct searches that incorporate the effects of eccentricity, precession or target light sources (e.g. subsolar). We present a hierarchical scheme based on a reduced bases method to decrease the computational cost of conducting a matched-filter based search. Compared to the current methods, we estimate without any loss in sensitivity, a speedup by a factor of 18 for sources with signal-to-noise ratio (SNR) of at least , and a factor of for SNR of at least 5. Our method is dominated by linear operations which are highly parallelizable. Therefore, we implement our algorithm using graphical processing units (GPUs) and evaluate commercially motivated metrics to demonstrate the efficiency of GPUs in CBC searches. Our scheme can be extended to generic CBC searches and allows for efficient matched filtering using GPUs
Atomic Fermi gas in the trimerized Kagom\'e lattice at the filling 2/3
We study low temperature properties of an atomic spinless interacting Fermi
gas in the trimerized Kagom\'e lattice for the case of two fermions per trimer.
The system is described by a quantum spin 1/2 model on the triangular lattice
with couplings depending on bonds directions. Using exact diagonalizations we
show that the system exhibits non-standard properties of a {\it quantum
spin-liquid crystal}, combining a planar antiferromagnetic order with an
exceptionally large number of low energy excitations.Comment: 4 pages & 4 figures + 2 tables, better version of Fig.
Atomic Bose-Fermi mixtures in an optical lattice
A mixture of ultracold bosons and fermions placed in an optical lattice
constitutes a novel kind of quantum gas, and leads to phenomena, which so far
have been discussed neither in atomic physics, nor in condensed matter physics.
We discuss the phase diagram at low temperatures, and in the limit of strong
atom-atom interactions, and predict the existence of quantum phases that
involve pairing of fermions with one or more bosons, or, respectively, bosonic
holes. The resulting composite fermions may form, depending on the system
parameters, a normal Fermi liquid, a density wave, a superfluid liquid, or an
insulator with fermionic domains. We discuss the feasibility for observing such
phases in current experiments.Comment: 4 pages, 1 eps figure, misprints correcte
Finite-temperature ordering in a two-dimensional highly frustrated spin model
We investigate the classical counterpart of an effective Hamiltonian for a
strongly trimerized kagome lattice. Although the Hamiltonian only has a
discrete symmetry, the classical groundstate manifold has a continuous global
rotational symmetry. Two cases should be distinguished for the sign of the
exchange constant. In one case, the groundstate has a 120^\circ spin structure.
To determine the transition temperature, we perform Monte-Carlo simulations and
measure specific heat, the order parameter as well as the associated Binder
cumulant. In the other case, the classical groundstates are macroscopically
degenerate. A thermal order-by-disorder mechanism is predicted to select
another 120^\circ spin-structure. A finite but very small transition
temperature is detected by Monte-Carlo simulations using the exchange method.Comment: 11 pages including 9 figures, uses IOP style files; to appear in J.
Phys.: Condensed Matter (proceedings of HFM2006
A stochastic template bank for gravitational wave searches for precessing neutron star - black hole coalescence events
Gravitational wave searches to date have largely focused on non-precessing systems. Including precession effects greatly increases the number of templates to be searched over. This leads to a corresponding increase in the computational cost and can increase the false alarm rate of a realistic search. On the other hand, there might be astrophysical systems that are entirely missed by non-precessing searches. In this paper we consider the problem of constructing a template bank using stochastic methods for neutron star - black hole binaries allowing for generic precession, but with the restriction that the total angular momentum of the binary is pointing towards the detector. We quantify the number of templates required for the search, and we explicitly construct the template bank. We show that despite the large number of templates, stochastic methods can be adapted to solve the problem. We quantify the parameter space region over which the non-precessing search might miss signals
The metabolic landscape browser:a novel tool for understanding pan-cancer metabolic processes through variance in gene expression data
The metabolic landscape browser:a novel tool for understanding pan-cancer metabolic processes through variance in gene expression data
The metabolic landscape browser:a novel tool for understanding pan-cancer metabolic processes through variance in gene expression data
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