6,014 research outputs found
The anisotropic XY model on the inhomogeneous periodic chain
The static and dynamic properties of the anisotropic XY-model on
the inhomogeneous periodic chain, composed of cells with different
exchange interactions and magnetic moments, in a transverse field are
determined exactly at arbitrary temperatures. The properties are obtained by
introducing the Jordan-Wigner fermionization and by reducing the problem to a
diagonalization of a finite matrix of order. The quantum transitions are
determined exactly by analyzing, as a function of the field, the induced
magnetization 1/n\sum_{m=1}^{n}\mu_{m}\left ( denotes
the cell, the site within the cell, the magnetic moment at site
within the cell) and the spontaneous magnetization which is obtained from the correlations for large spin separations. These results,
which are obtained for infinite chains, correspond to an extension of the ones
obtained by Tong and Zhong(\textit{Physica B} \textbf{304,}91 (2001)). The
dynamic correlations, , and the dynamic
susceptibility, are also obtained at arbitrary
temperatures. Explicit results are presented in the limit T=0, where the
critical behaviour occurs, for the static susceptibility as
a function of the transverse field , and for the frequency dependency of
dynamic susceptibility .Comment: 33 pages, 13 figures, 01 table. Revised version (minor corrections)
accepted for publiction in Phys. Rev.
Nuclear shadowing from exclusive quarkonium photoproduction at the BNL RHIC and CERN LHC
The photonuclear production of vector mesons in ultraperipheral heavy ion
collisions is investigated within the collinear approach using different
parameterizations for the nuclear gluon distribution. The integrated cross
section and the rapidity distribution for the () process are computed for energies of RHIC and LHC. A comparison with
the recent PHENIX data on coherent production of mesons is also
presented. We demonstrate that the study of the exclusive quarkonium
photoproduction can be used to constrain the nuclear effects in the gluon
distribution.Comment: 8 pages, 4 figures, 2 tables. Version to be published in Physical
Review
No-horizon theorem for spacetimes with spacelike G1 isometry groups
We consider four-dimensional spacetimes which obey the
Einstein equations , and admit a global spacelike
isometry group. By means of dimensional reduction and local
analyis on the reduced (2+1) spacetime, we obtain a sufficient condition on
which guarantees that cannot contain apparent
horizons. Given any (3+1) spacetime with spacelike translational isometry, the
no-horizon condition can be readily tested without the need for dimensional
reduction. This provides thus a useful and encompassing apparent horizon test
for -symmetric spacetimes. We argue that this adds further evidence
towards the validity of the hoop conjecture, and signals possible violations of
strong cosmic censorship.Comment: 8 pages, LaTeX, uses IOP package; published in Class. Quantum Gra
Alimentos volumosos para o perÃodo seco - I: silagem de girassol.
O objetivo desta publicação é reunir as principais informações relacionadas à silagem de girassol e, dessa forma, servir como embasamento para técnicos e produtores acerca da produção e conservação de uma opção de alimento volumoso de bom valor nutritivo.bitstream/CPAP/55979/1/DOC72.pdfFormato Eletrônic
Development of a temporary marker for peptides
3-[(N,N-dimethylaminophenyl)-4'-diazenyl]-benzoic acid was coupled with several amino acid esters and the product further acylated with Boc. The material thus obtained was then submitted to cleavage by electrolysis and nucleophilic attack in order to evaluate the possibility to use this chromophore as a temporary marker
Crossover to the KPZ equation
We characterize the crossover regime to the KPZ equation for a class of
one-dimensional weakly asymmetric exclusion processes. The crossover depends on
the strength asymmetry () and it occurs at
. We show that the density field is a solution of an
Ornstein-Uhlenbeck equation if , while for it is
an energy solution of the KPZ equation. The corresponding crossover for the
current of particles is readily obtained.Comment: Published by Annales Henri Poincare Volume 13, Number 4 (2012),
813-82
Avaliação da dormência em acessos precoces do bag amendoim.
Sementes de amendoim apresentam dormência em diferentes graus, sendo esta caracterÃstica mais pronunciada na subespécie hypogaea e em variedades de ciclo mais longo. A dormência é interessante do ponto de visto agronômico por evitar perdas durante a colheita e por estar relacionada à menor contaminação por aflatoxinas. Trinta e três acessos, com ciclo entre 90 e 100 dias, do Banco Ativo de Germoplasma de Amendoim foram avaliados quanto à dormência das sementes 14 dias após a colheita. Vinte sementes de cada acesso, tratadas com fungicida, foram dispostas em papel germitest umedecido em incubadas a 30 oC em germinador no Laboratório de Qualidade de Sementes da Embrapa Arroz e Feijão
New data on the distribution and conservation status of some angiosperms of the Cape Verde Islands, W Africa
New data on the distributibn and conservation status of some
angiosperms of the Cape Verde Islands, W Africa
Intensive field work aud analysis of the state of biodiversity ou all islands during the years iYY.3
lo IYYY Icd lo lhc publication ol’several contributions lo the flora and vegelalion of the archipclago
of Cabo Verde (Brochniann & al. 1997, Gornes & Vera-Cruz 1993. Gonles & al. I9YSa-h.
1998, Games 1997. Kilian & Leyens 1994, Leyens 1998. Leyens & Lobin 1995, Lobin & al.
1995) as well as to the compilation of the First Red Data List for the Cape Verde Islnuds (Lcyrus
& Lobin 1996). the elaboration of the National Strategy for Biodiversity Conservation (SIPA
19YY) and ! compilation of all areas in urgent need of protection (Leyens unpubl. diplonla thc.\is
IYYJ. Gwnes & al. iu prep.). As part UC the activities of the lnstituto National de Invcstig;uo t ISE) iutcnsive t’icld studies were conducted PI many diffcrctu localilics OII xcvcr;~I
islands. resulting in a thesis tGo~nes IY97) and several terminal study papers (Luz IYYY. Cosi;t
1994. Gonsalvez 1999). The results show that the vegetation and flora of the islands arc still IWI
fully known and much more field work is needed.
hllhot~gh Sanliiqw is one of lhc islands whcrc lhc firs1 holanicill iIlVcxligilliollx wcrr c:crriul
WI (Wcbh 1x49. Schruidt 1x52. Chcvalicr IY35) and where uu~ny intensive field studirs wcr
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