2,707 research outputs found
Aharonov-Anandan phase in Lipkin-Meskov-Glick model
In the system of several interacting spins, geometric phases have been
researched intensively.However, the studies are mainly focused on the adiabatic
case (Berry phase), so it is necessary for us to study the non-adiabatic
counterpart (Aharonov and Anandan phase). In this paper, we analyze both the
non-degenerate and degenerate geometric phase of Lipkin-Meskov-Glick type
model, which has many application in Bose-Einstein condensates and entanglement
theory. Furthermore, in order to calculate degenerate geometric phases, the
Floquet theorem and decomposition of operator are generalized. And the general
formula is achieved
Rhigonema trichopeplum sp. n. (Nematoda : Rhigonematidae), parasite of a millipede (Diplopoda : Spirobolida) from Myanmar
Une nouvelle espèce de parasite appartenant aux #Rhigonematidae, #Rhigonema trichopeplum sp. n., est décrite provenant de l'intestin d'un Spirobolide (#Diplopoda : #Spirobolida) indéterminé récolté au Myanmar. Cette nouvelle espèce est caractérisée par la combinaison de caractères suivante : corps de la femelle long d'environ 6,6 cm; pilosité cuticulaire limitée à la partie antérieure du corps; tractus génital femelle comportant un long vagin divisé en une région distale musculaire à paroi épaisse suivie par une chambre vaginale à paroi mince; volets advulvaires présents; diverticulum vaginal absent; queue de la femelle pourvue d'une lèvre anale postérieure nettement saillante; trois paires de papilles post-cloacales situées subdorsalement ou latéralement, mais non subventralement. Des photographies au microscope électronique à balayage de la région cervicale et de la queue de la femelle complètent la description. (Résumé d'auteur
Rhigonematida from New Britain diplopods : 1. The genus Carnoya Gilson, 1898 (Ransomnematoidea : Carnoyidae) with descriptions of three new species
Le genre #Carnoya Gilson, 1898 est défini et une liste des ses espèces nominales établie. Trois nouvelles espèces extraites de Diplopodes Spirobolides provenant de l'île de Nouvelle-Bretagne sont décrites et illustrées, y compris au MEB. #C. caputbulla sp. n. est caractérisé par la région céphalique femelle présentant un anneau en bouton, la forme nombre (onze) de papilles réduites supplémentaires et leur répartition, l'annélation de la région cervicale du mâle laquelle n'est pas renforcée, la queue extrêmement longue et les larges anneaux chez les deux sexes. #C. posterovulva sp. n. est caractérisé par l'anneau cervical en bouton de la femelle, la position postérieure unique de la vulve, la présence d'épines cervicales chez la femelle, la position des onze papilles copulatrices réduites, l'annélation de la région cervicale du mâle, la présence d'un seul collier céphalique de seize épines bien séparées chez le mâle, la queue extrêmement longue et les larges anneaux chez les deux sexes. #C. janiceae sp. n. est caractérisé par la région céphalique femelle sans anneau en ailes latérales au niveau du cloaque chez le mâle, la disposition des treize papilles mâles, l'annélation de la région cervicale du mâle, laquelle n'est pas renforcée, la longue queue et les larges anneaux chez les deux sexes. La taxonomie du genre et la valeur de certains caractères morphologiques sont discutées et les espèces des Amériques et de la région Australasie/Pacifique sont comparées et différenciées. (Résumé d'auteur
Statistical and Dynamical Study of Disease Propagation in a Small World Network
We study numerically statistical properties and dynamical disease propagation
using a percolation model on a one dimensional small world network. The
parameters chosen correspond to a realistic network of school age children. We
found that percolation threshold decreases as a power law as the short cut
fluctuations increase. We found also the number of infected sites grows
exponentially with time and its rate depends logarithmically on the density of
susceptibles. This behavior provides an interesting way to estimate the
serology for a given population from the measurement of the disease growing
rate during an epidemic phase. We have also examined the case in which the
infection probability of nearest neighbors is different from that of short
cuts. We found a double diffusion behavior with a slower diffusion between the
characteristic times.Comment: 12 pages LaTex, 10 eps figures, Phys.Rev.E Vol. 64, 056115 (2001
Open String Star as a Continuous Moyal Product
We establish that the open string star product in the zero momentum sector
can be described as a continuous tensor product of mutually commuting two
dimensional Moyal star products. Let the continuous variable parametrize the eigenvalues of the Neumann matrices; then the
noncommutativity parameter is given by .
For each , the Moyal coordinates are a linear combination of even
position modes, and the Fourier transform of a linear combination of odd
position modes. The commuting coordinate at is identified as the
momentum carried by half the string. We discuss the relation to Bars' work, and
attempt to write the string field action as a noncommutative field theory.Comment: 30 pages, LaTeX. One reference adde
Star Algebra Spectroscopy
The spectrum of the infinite dimensional Neumann matrices M^{11}, M^{12} and
M^{21} in the oscillator construction of the three-string vertex determines key
properties of the star product and of wedge and sliver states. We study the
spectrum of eigenvalues and eigenvectors of these matrices using the derivation
K_1 = L_1 + L_{-1} of the star algebra, which defines a simple infinite matrix
commuting with the Neumann matrices. By an exact calculation of the spectrum of
K_1, and by consideration of an operator generating wedge states, we are able
to find analytic expressions for the eigenvalues and eigenvectors of the
Neumann matrices and for the spectral density. The spectrum of M^{11} is
continuous in the range [-1/3, 0) with degenerate twist even and twist odd
eigenvectors for every eigenvalue except for -1/3.Comment: LaTeX, 30 pages, 2 figure
Siegel Gauge in Vacuum String Field Theory
We study the star algebra of ghost sector in vacuum string field theory
(VSFT). We show that the star product of two states in the Siegel gauge is BRST
exact if we take the BRST charge to be the one found in hep-th/0108150, and the
BRST exact states are nil factors in the star algebra. By introducing a new
star product defined on the states in the Siegel gauge, the equation of motion
of VSFT is characterized as the projection condition with respect to this new
product. We also comment on the comma form of string vertex in the ghost
sector.Comment: 13 pages, lanlmac; v3: comment adde
Ghost Kinetic Operator of Vacuum String Field Theory
Using the data of eigenvalues and eigenvectors of Neumann matrices in the
3-string vertex, we prove analytically that the ghost kinetic operator of
vacuum string field theory obtained by Hata and Kawano is equal to the ghost
operator inserted at the open string midpoint. We also comment on the values of
determinants appearing in the norm of sliver state.Comment: 19 pages, 1 figure, lanlmac; v2: typos correcte
The Spectrum of the Neumann Matrix with Zero Modes
We calculate the spectrum of the matrix M' of Neumann coefficients of the
Witten vertex, expressed in the oscillator basis including the zero-mode a_0.
We find that in addition to the known continuous spectrum inside [-1/3,0) of
the matrix M without the zero-modes, there is also an additional eigenvalue
inside (0,1). For every eigenvalue, there is a pair of eigenvectors, a
twist-even and a twist-odd. We give analytically these eigenvectors as well as
the generating function for their components. Also, we have found an
interesting critical parameter b_0 = 8 ln 2 on which the forms of the
eigenvectors depend.Comment: 25+1 pages, 3 Figures; typos corrected and some comments adde
S matrix of collective field theory
By applying the Lehmann-Symanzik-Zimmermann (LSZ) reduction formalism, we
study the S matrix of collective field theory in which fermi energy is larger
than the height of potential. We consider the spatially symmetric and
antisymmetric boundary conditions. The difference is that S matrices are
proportional to momenta of external particles in antisymmetric boundary
condition, while they are proportional to energies in symmetric boundary
condition. To the order of , we find simple formulas for the S matrix
of general potential. As an application, we calculate the S matrix of a case
which has been conjectured to describe a "naked singularity".Comment: 19 page, LaTe
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