1,655 research outputs found
Magnetic phase diagram of three-dimensional diluted Ising antiferromagnet NiMg(OH)
- diagram of 3D diluted Ising antiferromagnet
NiMg(OH) with = 0.8 has been determined from
measurements of SQUID DC magnetization and AC magnetic susceptibility. At =
0, this compound undergoes two magnetic phase transitions: an antiferromagnetic
(AF) transition at the N\'{e}el temperature (= 20.7 K) and a reentrant
spin glass (RSG) transition at ( 6 K). The - diagram
consists of the RSG, spin glass (SG), and AF phases. These phases meet a
multicritical point ( = 42 kOe, = 5.6 K). The
irreversibility of susceptibility defined by (= ) shows a negative local minimum for 10 35 kOe,
suggesting the existence of possible glassy phase in the AF phase. A broad peak
in and at 20 kOe for (= 26.4 K) suggests the existence of the Griffiths
phase.Comment: 11 pages, 14 figures; J. Phys. Soc. Jpn. 73 (2004) No. 1 issue, in
pres
Threshold Analysis of Non-Binary Spatially-Coupled LDPC Codes with Windowed Decoding
In this paper we study the iterative decoding threshold performance of
non-binary spatially-coupled low-density parity-check (NB-SC-LDPC) code
ensembles for both the binary erasure channel (BEC) and the binary-input
additive white Gaussian noise channel (BIAWGNC), with particular emphasis on
windowed decoding (WD). We consider both (2,4)-regular and (3,6)-regular
NB-SC-LDPC code ensembles constructed using protographs and compute their
thresholds using protograph versions of NB density evolution and NB extrinsic
information transfer analysis. For these code ensembles, we show that WD of
NB-SC-LDPC codes, which provides a significant decrease in latency and
complexity compared to decoding across the entire parity-check matrix, results
in a negligible decrease in the near-capacity performance for a sufficiently
large window size W on both the BEC and the BIAWGNC. Also, we show that
NB-SC-LDPC code ensembles exhibit gains in the WD threshold compared to the
corresponding block code ensembles decoded across the entire parity-check
matrix, and that the gains increase as the finite field size q increases.
Moreover, from the viewpoint of decoding complexity, we see that (3,6)-regular
NB-SC-LDPC codes are particularly attractive due to the fact that they achieve
near-capacity thresholds even for small q and W.Comment: 6 pages, 8 figures; submitted to 2014 IEEE International Symposium on
Information Theor
Choreographic Three Bodies on the Lemniscate
We show that choreographic three bodies {x(t), x(t+T/3), x(t-T/3)} of period
T on the lemniscate, x(t) = (x-hat+y-hat cn(t))sn(t)/(1+cn^2(t)) parameterized
by the Jacobi's elliptic functions sn and cn with modulus k^2 = (2+sqrt{3})/4,
conserve the center of mass and the angular momentum, where x-hat and y-hat are
the orthogonal unit vectors defining the plane of the motion. They also
conserve the moment of inertia, the kinetic energy, the sum of square of the
curvature, the product of distance and the sum of square of distance between
bodies. We find that they satisfy the equation of motion under the potential
energy sum_{i<j}(1/2 ln r_{ij} -sqrt{3}/24 r_{ij}^2) or sum_{i<j}1/2 ln r_{ij}
-sum_{i}sqrt{3}/8 r_{i}^2, where r_{ij} the distance between the body i and j,
and r_{i} the distance from the origin. The first term of the potential
energies is the Newton's gravity in two dimensions but the second term is the
mutual repulsive force or a repulsive force from the origin, respectively.
Then, geometric construction methods for the positions of the choreographic
three bodies are given
On Existence of a Biorthonormal Basis Composed of Eigenvectors of Non-Hermitian Operators
We present a set of necessary conditions for the existence of a biorthonormal
basis composed of eigenvectors of non-Hermitian operators. As an illustration,
we examine these conditions in the case of normal operators. We also provide a
generalization of the conditions which is applicable to non-diagonalizable
operators by considering not only eigenvectors but also all root vectors.Comment: 6 pages, no figures; (v2) minor revisions based on the comment
quant-ph/0603096; (v3) presentation improved, final version to appear in
Journal of Physics
Domain walls with non-Abelian orientational moduli
Domain walls with non-Abelian orientational moduli are constructed in U(N)
gauge theories coupled to Higgs scalar fields with degenerate masses. The
associated global symmetry is broken by the domain walls, resulting in the
Nambu-Goldstone (and quasi-Nambu-Goldstone) bosons, which form the non-Abelian
orientational moduli. As walls separate, the wave functions of the non-Abelian
orientational moduli spread between domain walls. By taking the limit of Higgs
mass differences to vanish, we clarify the convertion of wall position moduli
into the non-Abelian orientational moduli. The moduli space metric and its
Kahler potential of the effective field theory on the domain walls are
constructed. We consider two models: a U(1) gauge theory with several charged
Higgs fields, and a U(N) gauge theory with 2N Higgs fields in the fundamental
representation. More details are found in our paper published in Phys. Rev. D77
(2008) 125008 [arXiv:0802.3135 [hep-th]].Comment: contribution to the Proceedings of he 1st MCCQG conference at Crete,
sept. 2009, to appear in Journal of Physics: Conference Series of IO
Field Theoretical Analysis of On-line Learning of Probability Distributions
On-line learning of probability distributions is analyzed from the field
theoretical point of view. We can obtain an optimal on-line learning algorithm,
since renormalization group enables us to control the number of degrees of
freedom of a system according to the number of examples. We do not learn
parameters of a model, but probability distributions themselves. Therefore, the
algorithm requires no a priori knowledge of a model.Comment: 4 pages, 1 figure, RevTe
Dynamics of Non-Abelian Vortices
The scattering is studied using moduli space metric for well-separated
vortices of non-Abelian vortices in (2+1)-dimensional U(N) gauge theories with
N Higgs fields in the fundamental representation. Unlike vortices in the
Abelian-Higgs model, dynamics of non-Abelian vortices has a lot of new
features; The kinetic energy in real space can be transfered to that of
internal orientational moduli and vice versa, the energy and charge transfer
between two vortices, the scattering angle of collisions with a fixed impact
parameter depends on the internal orientations, and some resonances appear due
to synchronization of the orientations. Scattering of dyonic non-Abelian
vortices in a mass deformed theory is also studied. We find a bound state of
two vortices moving along coils around a circle, like a loop of a phone code.Comment: 45 pages, 13 figure
Statistical mechanics of lossy compression for non-monotonic multilayer perceptrons
A lossy data compression scheme for uniformly biased Boolean messages is
investigated via statistical mechanics techniques. We utilize tree-like
committee machine (committee tree) and tree-like parity machine (parity tree)
whose transfer functions are non-monotonic. The scheme performance at the
infinite code length limit is analyzed using the replica method. Both committee
and parity treelike networks are shown to saturate the Shannon bound. The AT
stability of the Replica Symmetric solution is analyzed, and the tuning of the
non-monotonic transfer function is also discussed.Comment: 29 pages, 7 figure
Expression profiles of urbilaterian genes uniquely shared between honey bee and vertebrates
<p>Abstract</p> <p>Background</p> <p>Large-scale comparison of metazoan genomes has revealed that a significant fraction of genes of the last common ancestor of Bilateria (Urbilateria) is lost in each animal lineage. This event could be one of the underlying mechanisms involved in generating metazoan diversity. However, the present functions of these ancient genes have not been addressed extensively. To understand the functions and evolutionary mechanisms of such ancient Urbilaterian genes, we carried out comprehensive expression profile analysis of genes shared between vertebrates and honey bees but not with the other sequenced ecdysozoan genomes (honey bee-vertebrate specific, HVS genes) as a model.</p> <p>Results</p> <p>We identified 30 honey bee and 55 mouse HVS genes. Many HVS genes exhibited tissue-selective expression patterns; intriguingly, the expression of 60% of honey bee HVS genes was found to be brain enriched, and 24% of mouse HVS genes were highly expressed in either or both the brain and testis. Moreover, a minimum of 38% of mouse HVS genes demonstrated neuron-enriched expression patterns, and 62% of them exhibited expression in selective brain areas, particularly the forebrain and cerebellum. Furthermore, gene ontology (GO) analysis of HVS genes predicted that 35% of genes are associated with DNA transcription and RNA processing.</p> <p>Conclusion</p> <p>These results suggest that HVS genes include genes that are biased towards expression in the brain and gonads. They also demonstrate that at least some of Urbilaterian genes retained in the specific animal lineage may be selectively maintained to support the species-specific phenotypes.</p
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