169 research outputs found
The ground state properties of the spin-1/2 transverse Ising chain with periodically varying bonds and fields
Using continued fractions we study the ground state properties of the
spin-1/2 Ising chain in a transverse field with periodically varying
interaction strengths and external fields. We consider in detail the chain
having the period of modulation of interactions equals 2 and compare the
results obtained with those corresponding to the spin-1/2 isotropic XY chain in
a transverse field. In contrast to the behaviour of the transverse XY chain,
the transverse Ising chain does not exhibit a step-like magnetization vs. field
dependence caused by the alternation of bonds, its susceptibility exhibits a
logarithmic singularity at the field determined by interaction strengths, and
it is stable with respect to spin-Peierls dimerization.Comment: 11 pages, latex, 4 figure
On the connection between gamma and radio radiation spectra in pulsars
The model of pulsar radio emission is discussed in which a coherent radio
emis-sion is excited in a vacuum gap above polar cap of neutron star. Pulsar X
and gamma radiation are considered as the result of low-frequency radio
emission inverse Comp-ton scattering on ultra relativistic electrons
accelerated in the gap. The influence of the pulsar magnetic field on Compton
scattering is taken into account. The relation of radio and gamma radiation
spectra has been found in the framework of the model.Comment: 15 pages, 3 figures, Russian version accepted to JETP, partly
published in JETP Letters, Vol. 85, #6 (2007
Acoustic Cyclotron Resonance and Giant High Frequency Magnetoacoustic Oscillations in Metals with Locally Flattened Fermi Surface
We consider the effect of local flattening on the Fermi surface (FS) of a
metal upon geometric oscillations of the velocity and attenuation of ultrasonic
waves in the neighborhood of the acoustic cyclotron resonance. It is shown that
such peculiarities of the local geometry of the FS can lead to a significant
enhancement of both cyclotron resonance and geometric oscillations.
Characteristic features of the coupling of ultrasound to shortwave cyclotron
waves arising due to the local flattening of the FS are analyzed.
PACS numbers 71.18.+y; 72.15.Gd; 72.15.-vComment: 8 pages, 3 figures, text revise
New symmetries of the chiral Potts model
In this paper a hithertho unknown symmetry of the three-state chiral Potts
model is found consisting of two coupled Temperley-Lieb algebras. From these we
can construct new superintegrable models. One realisation is in terms of a
staggered isotropic XY spin chain. Further we investigate the importance of the
algebra for the existence of mutually commuting charges. This leads us to a
natural generalisation of the boost-operator, which generates the charges.Comment: 19 pages, improved notation, made the text easier to read, corrected
some typo
Implications of a Nonthermal Origin of the Excess EUV Emission from the Coma Cluster of Galaxies
The inverse Compton (IC) interpretation of the excess EUV emission, that was
recently reported from several clusters of galaxies, suggests that the amount
of relativistic electrons in the intracluster medium is highly significant,
W_e>10^{61} erg. Considering Coma as the prototype galaxy cluster of nonthermal
radiation, we discuss implications of the inverse Compton origin of the excess
EUV fluxes in the case of low intracluster magnetic fields of order 0.1 muG, as
required for the IC interpretation of the observed excess hard X-ray flux, and
in the case of high fields of order 1 muG as suggested by Faraday rotation
measurements. Although for such high intracluster fields the excess hard X-rays
will require an explanation other than by the IC effect, we show that the
excess EUV flux can be explained by the IC emission of a `relic' population of
electrons driven into the incipient intracluster medium at the epoch of
starburst activity by galactic winds, and later on reenergized by adiabatic
compression and/or large-scale shocks transmitted through the cluster as the
consequence of more recent merger events. For high magnetic fields B > 1 muG
the interpretation of the radio fluxes of Coma requires a second population of
electrons injected recently. They can be explained as secondaries produced by a
population of relativistic protons. We calculate the fluxes of gamma-rays to be
expected in both the low and high magnetic field scenarios, and discuss
possibilities to distinguish between these two principal options by future
gamma-ray observations.Comment: LaTeX, 6 figures; accepted for publication in Ap
Electron-lattice kinetics of metals heated by ultrashort laser pulses
We propose a kinetic model of transient nonequilibrium phenomena in metals
exposed to ultrashort laser pulses when heated electrons affect the lattice
through direct electron-phonon interaction. This model describes the
destruction of a metal under intense laser pumping. We derive the system of
equations for the metal, which consists of hot electrons and a cold lattice.
Hot electrons are described with the help of the Boltzmann equation and
equation of thermoconductivity. We use the equations of motion for lattice
displacements with the electron force included. The lattice deformation is
estimated immediately after the laser pulse up to the time of electron
temperature relaxation. An estimate shows that the ablation regime can be
achieved.Comment: 7 pages; Revtex. to appear in JETP 88, #1 (1999
Central factorials under the Kontorovich-Lebedev transform of polynomials
We show that slight modifications of the Kontorovich-Lebedev transform lead
to an automorphism of the vector space of polynomials. This circumstance along
with the Mellin transformation property of the modified Bessel functions
perform the passage of monomials to central factorial polynomials. A special
attention is driven to the polynomial sequences whose KL-transform is the
canonical sequence, which will be fully characterized. Finally, new identities
between the central factorials and the Euler polynomials are found.Comment: also available at http://cmup.fc.up.pt/cmup/ since the 2nd August
201
Hydrodynamic Stability Analysis of Burning Bubbles in Electroweak Theory and in QCD
Assuming that the electroweak and QCD phase transitions are first order, upon
supercooling, bubbles of the new phase appear. These bubbles grow to
macroscopic sizes compared to the natural scales associated with the Compton
wavelengths of particle excitations. They propagate by burning the old phase
into the new phase at the surface of the bubble. We study the hydrodynamic
stability of the burning and find that for the velocities of interest for
cosmology in the electroweak phase transition, the shape of the bubble wall is
stable under hydrodynamic perturbations. Bubbles formed in the cosmological QCD
phase transition are found to be a borderline case between stability and
instability.Comment: preprint # SLAC-PUB-5943, SCIPP 92/56 38 pages, 10 figures (submitted
via `uufiles'), phyzzx format minor snafus repaire
Boundary conditions in the Unruh problem
We have analyzed the Unruh problem in the frame of quantum field theory and
have shown that the Unruh quantization scheme is valid in the double Rindler
wedge rather than in Minkowski spacetime. The double Rindler wedge is composed
of two disjoint regions (- and -wedges of Minkowski spacetime) which are
causally separated from each other. Moreover the Unruh construction implies
existence of boundary condition at the common edge of - and -wedges in
Minkowski spacetime. Such boundary condition may be interpreted as a
topological obstacle which gives rise to a superselection rule prohibiting any
correlations between - and - Unruh particles. Thus the part of the field
from the -wedge in no way can influence a Rindler observer living in the
-wedge and therefore elimination of the invisible "left" degrees of freedom
will take no effect for him. Hence averaging over states of the field in one
wedge can not lead to thermalization of the state in the other. This result is
proved both in the standard and algebraic formulations of quantum field theory
and we conclude that principles of quantum field theory does not give any
grounds for existence of the "Unruh effect".Comment: 31 pages,1 figur
Evaluation of a candidate breast cancer associated SNP in ERCC4 as a risk modifier in BRCA1 and BRCA2 mutation carriers. Results from the Consortium of Investigators of Modifiers of BRCA1/BRCA2 (CIMBA)
Background: In this study we aimed to evaluate the role of a SNP in intron 1 of the ERCC4 gene (rs744154), previously reported to be associated with a reduced risk of breast cancer in the general population, as a breast cancer risk modifier in BRCA1 and BRCA2 mutation carriers. Methods: We have genotyped rs744154 in 9408 BRCA1 and 5632 BRCA2 mutation carriers from the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA) and assessed its association with breast cancer risk using a retrospective weighted cohort approach. Results: We found no evidence of association with breast cancer risk for BRCA1 (per-allele HR: 0.98, 95% CI: 0.93–1.04, P=0.5) or BRCA2 (per-allele HR: 0.97, 95% CI: 0.89–1.06, P=0.5) mutation carriers. Conclusion: This SNP is not a significant modifier of breast cancer risk for mutation carriers, though weak associations cannot be ruled out. A Osorio1, R L Milne2, G Pita3, P Peterlongo4,5, T Heikkinen6, J Simard7, G Chenevix-Trench8, A B Spurdle8, J Beesley8, X Chen8, S Healey8, KConFab9, S L Neuhausen10, Y C Ding10, F J Couch11,12, X Wang11, N Lindor13, S Manoukian4, M Barile14, A Viel15, L Tizzoni5,16, C I Szabo17, L Foretova18, M Zikan19, K Claes20, M H Greene21, P Mai21, G Rennert22, F Lejbkowicz22, O Barnett-Griness22, I L Andrulis23,24, H Ozcelik24, N Weerasooriya23, OCGN23, A-M Gerdes25, M Thomassen25, D G Cruger26, M A Caligo27, E Friedman28,29, B Kaufman28,29, Y Laitman28, S Cohen28, T Kontorovich28, R Gershoni-Baruch30, E Dagan31,32, H Jernström33, M S Askmalm34, B Arver35, B Malmer36, SWE-BRCA37, S M Domchek38, K L Nathanson38, J Brunet39, T RamĂłn y Cajal40, D Yannoukakos41, U Hamann42, HEBON37, F B L Hogervorst43, S Verhoef43, EB GĂłmez GarcĂa44,45, J T Wijnen46,47, A van den Ouweland48, EMBRACE37, D F Easton49, S Peock49, M Cook49, C T Oliver49, D Frost49, C Luccarini50, D G Evans51, F Lalloo51, R Eeles52, G Pichert53, J Cook54, S Hodgson55, P J Morrison56, F Douglas57, A K Godwin58, GEMO59,60,61, O M Sinilnikova59,60, L Barjhoux59,60, D Stoppa-Lyonnet61, V Moncoutier61, S Giraud59, C Cassini62,63, L Olivier-Faivre62,63, F RĂ©villion64, J-P Peyrat64, D Muller65, J-P Fricker65, H T Lynch66, E M John67, S Buys68, M Daly69, J L Hopper70, M B Terry71, A Miron72, Y Yassin72, D Goldgar73, Breast Cancer Family Registry37, C F Singer74, D Gschwantler-Kaulich74, G Pfeiler74, A-C Spiess74, Thomas v O Hansen75, O T Johannsson76, T Kirchhoff77, K Offit77, K Kosarin77, M Piedmonte78, G C Rodriguez79, K Wakeley80, J F Boggess81, J Basil82, P E Schwartz83, S V Blank84, A E Toland85, M Montagna86, C Casella87, E N Imyanitov88, A Allavena89, R K Schmutzler90, B Versmold90, C Engel91, A Meindl92, N Ditsch93, N Arnold94, D Niederacher95, H DeiĂźler96, B Fiebig97, R Varon-Mateeva98, D Schaefer99, U G Froster100, T Caldes101, M de la Hoya101, L McGuffog49, A C Antoniou49, H Nevanlinna6, P Radice4,5 and J BenĂtez1,3 on behalf of CIMB
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