1,359 research outputs found
Correlation functions for time-dependent calculation of linear-response functions
We emphasize the importance of choosing an appropriate correlation function
to reduce numerical errors in calculating the linear-response function as a
Fourier transformation of a time-dependent correlation function. As an example
we take dielectric functions of silicon crystal calculated with a
time-dependent method proposed by Iitaka et al. [Phys. Rev. E 56, 1222 (1997)].Comment: to be published in Phys.Rev.E 01 Dec 1997, 2 pages, 4 figures, more
information at http://espero.riken.go.jp
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
Exact Supersymmetric Amplitude for \kkb\/ and \bbb\/ Mixing
We present the most general supersymmetric amplitude for \kkb\/ and \bbb\/
mixing resulting from gluino box diagrams. We use this amplitude to place
general constraints on the magnitude of flavor-changing squark mass mixings,
and compare these constraints to theoretical predictions both in and beyond the
Minimal Supersymmetric Standard Model.Comment: 11 pages plus 2 figures available on request, MIU-THP-92/6
Soliton Trap in Strained Graphene Nanoribbons
The wavefunction of a massless fermion consists of two chiralities,
left-handed and right-handed, which are eigenstates of the chiral operator. The
theory of weak interactions of elementally particle physics is not symmetric
about the two chiralities, and such a symmetry breaking theory is referred to
as a chiral gauge theory. The chiral gauge theory can be applied to the
massless Dirac particles of graphene. In this paper we show within the
framework of the chiral gauge theory for graphene that a topological soliton
exists near the boundary of a graphene nanoribbon in the presence of a strain.
This soliton is a zero-energy state connecting two chiralities and is an
elementally excitation transporting a pseudospin. The soliton should be
observable by means of a scanning tunneling microscopy experiment.Comment: 7 pages, 4 figure
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
A note on quantization operators on Nichols algebra model for Schubert calculus on Weyl groups
We give a description of the (small) quantum cohomology ring of the flag
variety as a certain commutative subalgebra in the tensor product of the
Nichols algebras. Our main result can be considered as a quantum analog of a
result by Y. Bazlov
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
Nonlinearity-Tolerant Modulation Formats for Coherent Optical Communications
Fiber nonlinearity is the main factor limiting the transmission distance of coherent optical communications. We overview several modulation formats intrinsically tolerant to fiber nonlinearity. We recently proposed family of 4D modulation formats based on 2-ary amplitude 8-ary phase-shift keying (2A8PSK), covering the spectral efficiency of 5, 6, and 7 bits/4D symbol, which will be explained in detail in this chapter. These coded modulation formats fill the gap of spectral efficiency between DP-QPSK and DP-16QAM, showing superb performance both in linear and nonlinear regimes. Since these modulation formats share the same constellation and use different parity bit expressions only, digital signal processing can accommodate those multiple modulation formats with minimum additional complexity. Nonlinear transmission simulations indicate that these modulation formats outperform the conventional formats at each spectral efficiency. We also review DSP algorithms and experimental results. Their application to time-domain hybrid modulation for 4–8 bits/4D symbol is also reviewed. Furthermore, an overview of an eight-dimensional 2A8PSK-based modulation format based on a Grassmann code is also given. All these results indicate that the 4D-2A8PSK family show great promise of excellent linear and nonlinear performances in the spectral efficiency between 3.5 and 8 bits/4D symbol
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