47,983 research outputs found
Solvable Lattice Gas Models with Three Phases
Phase boundaries in p-T and p-V diagrams are essential in material science
researches. Exact analytic knowledge about such phase boundaries are known so
far only in two-dimensional (2D) Ising-like models, and only for cases with two
phases. In the present paper we present several lattice gas models, some with
three phases. The phase boundaries are either analytically calculated or
exactly evaluated.Comment: 5 pages, 6 figure
Flavor-twisted boundary condition for simulations of quantum many-body systems
We present an approximative simulation method for quantum many-body systems
based on coarse graining the space of the momentum transferred between
interacting particles, which leads to effective Hamiltonians of reduced size
with the flavor-twisted boundary condition. A rapid, accurate, and fast
convergent computation of the ground-state energy is demonstrated on the
spin-1/2 quantum antiferromagnet of any dimension by employing only two sites.
The method is expected to be useful for future simulations and quick estimates
on other strongly correlated systems.Comment: 6 pages, 2 figure
Free-floating planets from core accretion theory: microlensing predictions
We calculate the microlensing event rate and typical time-scales for the
free-floating planet (FFP) population that is predicted by the core accretion
theory of planet formation. The event rate is found to be ~
of that for the stellar population. While the stellar microlensing event
time-scale peaks at around 20 days, the median time-scale for FFP events (~0.1
day) is much shorter. Our values for the event rate and the median time-scale
are significantly smaller than those required to explain the \cite{Sum+11}
result, by factors of ~13 and ~16, respectively. The inclusion of planets at
wide separations does not change the results significantly. This discrepancy
may be too significant for standard versions of both the core accretion theory
and the gravitational instability model to explain satisfactorily. Therefore,
either a modification to the planet formation theory is required, or other
explanations to the excess of short-time-scale microlensing events are needed.
Our predictions can be tested by ongoing microlensing experiment such as
KMTNet, and by future satellite missions such as WFIRST and Euclid.Comment: 6 pages, 5 figures, MNRAS in pres
The ordered K-theory of a full extension
Let A be a C*-algebra with real rank zero which has the stable weak
cancellation property. Let I be an ideal of A such that I is stable and
satisfies the corona factorization property. We prove that 0->I->A->A/I->0 is a
full extension if and only if the extension is stenotic and K-lexicographic. As
an immediate application, we extend the classification result for graph
C*-algebras obtained by Tomforde and the first named author to the general
non-unital case. In combination with recent results by Katsura, Tomforde, West
and the first author, our result may also be used to give a purely
K-theoretical description of when an essential extension of two simple and
stable graph C*-algebras is again a graph C*-algebra.Comment: Version IV: No changes to the text. We only report that Theorem 4.9
is not correct as stated. See arXiv:1505.05951 for more details. Since
Theorem 4.9 is an application to the main results of the paper, the main
results of this paper are not affected by the error. Version III comments:
Some typos and errors corrected. Some references adde
Invariant information and complementarity in high-dimensional states
Using a generalization of the invariant information introduced by Brukner and
Zeilinger [Phys. Rev. Lett. \textbf{83}, 3354 (1999)] to high-dimensional
systems, we introduce a complementarity relation between the local and nonlocal
information for systems under the isolated environment, where
is prime or the power of prime. We also analyze the dynamics of the local
information in the decoherence process.Comment: 4 pages, 2 figure
Luby Transform Coding Aided Iterative Detection for Downlink SDMA Systems
A Luby Transform (LT) coded downlink Spatial Division Multiple Access (SDMA) system using iterative detection is proposed, which invokes a low-complexity near-Maximum-Likelihood (ML) Sphere Decoder (SD). The Ethernet-based Internet section of the transmission chain inflicts random packet erasures, which is modelled by the Binary Erasure Channel (BEC), which the wireless downlink imposes both fading and noise. A novel log-Likelihood Ratio based packet reliability metric is used for identifying the channel-decoded packets, which are likely to be error-infested. Packets having residual errors must not be passed on to the KT decoder for the sake of avoiding LT-decoding âinduced error propagation. The proposed scheme is capable of maintaining an infinitesimally low packet error ratio in the downlink of the wireless Internet for Eb/n0 values in excess of about 3dB
Pair Distribution Function of One-dimensional "Hard Sphere" Fermi and Bose Systems
The pair distributions of one-dimensional "hard sphere" fermion and boson
systems are exactly evaluated by introducing gap variables.Comment: 4 page
A nonlocal eigenvalue problem and the stability of spikes for reaction-diffusion systems with fractional reaction rates
We consider a nonlocal eigenvalue problem which arises in the study of stability of spike solutions for reaction-diffusion systems with
fractional reaction rates such as the Sel'kov model, the
Gray-Scott system, the hypercycle Eigen and Schuster, angiogenesis, and the generalized Gierer-Meinhardt
system.
We give some sufficient and explicit conditions for stability
by studying the corresponding nonlocal eigenvalue problem in a new
range of parameters
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