34,058 research outputs found
Wigner Oscillators, Twisted Hopf Algebras and Second Quantization
By correctly identifying the role of central extension in the centrally
extended Heisenberg algebra h, we show that it is indeed possible to construct
a Hopf algebraic structure on the corresponding enveloping algebra U(h) and
eventually deform it through Drinfeld twist. This Hopf algebraic structure and
its deformed version U^F(h) are shown to be induced from a more fundamental
Hopf algebra obtained from the Schroedinger field/oscillator algebra and its
deformed version, provided that the fields/oscillators are regarded as
odd-elements of the super-algebra osp(1|2n). We also discuss the possible
implications in the context of quantum statistics.Comment: 23 page
The influence of statistical properties of Fourier coefficients on random surfaces
Many examples of natural systems can be described by random Gaussian
surfaces. Much can be learned by analyzing the Fourier expansion of the
surfaces, from which it is possible to determine the corresponding Hurst
exponent and consequently establish the presence of scale invariance. We show
that this symmetry is not affected by the distribution of the modulus of the
Fourier coefficients. Furthermore, we investigate the role of the Fourier
phases of random surfaces. In particular, we show how the surface is affected
by a non-uniform distribution of phases
Busca computacional por grupos de genes homólogos sob evidência de seleção positiva em Alphaherpesvirinae.
Este estudo detectou diversos genes virais sabidamente relacionados à modulação do sistema imune dos hospedeiros sob evidência de seleção positiva
Conservation laws and bosonization in integrable Luttinger liquids
We examine and explain the Luttinger-liquid character of models solvable by
the Bethe ansatz by introducing a suitable bosonic operator algebra. In the
case of the Hubbard chain, this involves two bosonic algebras which apply to
{\it all} values of , electronic density, and magnetization. Only at zero
magnetization does this lead to the usual charge - spin separation. We show
that our ``pseudoparticle'' operator approach clarifies, unifies, and extends
several recent results, including the existence of independent right and left
equations of motion and the concept of ``pseudoparticle'' (also known as
``Bethe quasiparticle'').Comment: 12 pages, RevTeX, preprint CSI
Estimativas de parâmetros genéticos e de ganhos direto e indireto à seleção para caracterÃsticas reprodutivas e de crescimento em um rebanho da raça Canchim
Neste trabalho, objetivou-se estimar as herdabilidades e as correlações genéticas entre os pesos ao nascimento (PN), à desmama (P240), ao ano (P365) e ao sobreano (P550), os ganhos de peso do nascimento à desmama (GND) e do nascimento ao sobreano (GN18), o número de dias para ganhar 175 kg do nascimento à desmama (D175) e para ganhar 450 kg do nascimento ao abate (D450) de machos e fêmeas, o peso adulto (PAD) de fêmeas em um rebanho da raça Canchim visando à definição de critérios de seleção. Foram realizadas análises unicaracteres e bicaracteres pelo método da máxima verossimilhança restrita livre de derivadas utilizando-se modelos estatÃsticos que incluÃram os efeitos fixos de ano e mês de nascimento, sexo do animal, ano e mês do parto, idade do animal ao parto e idade da mãe como covariável (efeitos linear e quadrático), além dos efeitos aleatórios aditivo direto e materno, de ambiente permanente e residual, dependendo da caracterÃstica. As estimativas de herdabilidade obtidas pelas análises unicaracteres foram iguais a 0,41 (PN), 0,28 (P240), 0,38 (P365), 0,28 (P550), 0,26 (GND), 0,30 (GN18), 0,23 (D175), 0,23 (D450) e 0,48 (PAD), enquanto as estimativas de correlação genética obtidas por análises bicaracteres variaram de 0,28 a 0,97 entre os pesos, de 0,11 a 0,97 entre pesos e ganhos de peso, de 0,00 a -0,98 entre pesos e dias para atingir determinado peso, e de -0,63 a -0,98 entre os ganhos de peso e dias para atingir determinado peso e iguais a 0,69 para GND e GN18 e 0,76 para D175 e D450. Estas estimativas sugerem a possibilidade de se obter progresso genético pela seleção para todas as caracterÃsticas estudadas e que a seleção para qualquer uma delas deverá provocar mudanças nas outras
Magnetic-field and chemical-potential effects on the low-energy separation
We show that in the presence of a magnetic field the usual low-energy
separation of the Hubbard chain is replaced by a ``'' and ``''
separation. Here and refer to small-momentum and low-energy independent
excitation modes which couple both to charge and spin. Importantly, we find the
exact generators of these excitations both in the electronic and pseudoparticle
basis. In the limit of zero magnetic field these generators become the usual
charge and spin fluctuation operators. The and elementary excitations
are associated with the and pseudoparticles, respectively. We also
study the separate pseudoparticle left and right conservation laws. In the
presence of the magnetic field the small-momentum and low-energy excitations
can be bosonized. However, the suitable bosonization corresponds to the and
pseudoparticle modes and not to the usual charge and spin fluctuations. We
evaluate exactly the commutator between the electronic-density operators. Its
spin-dependent factor is in general non diagonal and depends on the
interaction. The associate bosonic commutation relations characterize the
present unconventional low-energy separation.Comment: 29 pages, latex, submitted to Phys. Rev.
Brownian motion meets Riemann curvature
The general covariance of the diffusion equation is exploited in order to
explore the curvature effects appearing on brownian motion over a d-dimensional
curved manifold. We use the local frame defined by the so called Riemann normal
coordinates to derive a general formula for the mean-square geodesic distance
(MSD) at the short-time regime. This formula is written in terms of
invariants that depend on the Riemann curvature tensor. We study the
n-dimensional sphere case to validate these results. We also show that the
diffusion for positive constant curvature is slower than the diffusion in a
plane space, while the diffusion for negative constant curvature turns out to
be faster. Finally the two-dimensional case is emphasized, as it is relevant
for the single particle diffusion on biomembranes.Comment: 16 pages and 3 figure
Structural study of the interaction of vanadate with the ligand 1,2-dimethyl-3-hydroxy-4-pyridinone (Hdmpp) in aqueous solution
The interaction of vanadate with the ligand 1,2-dimethyl-3-hydroxy-4-pyridinone (Hdmpp) was studied in aqueous solution using a combination of multinuclear NMR and EPR spectroscopies, as well as potentiometry and cyclic voltammetry. The different species in solution were identified and characterized, and their pKa values and stability constants determined. The vanadium complexes formed in solution are strongly dependent on media composition (ionic strength, presence of buffer), pH and metal-to-ligand ratio (M:L). Two major species -- V(V)/dmpp and V(V)/(dmpp)2 -- are formed in a 140 mM NaCl solution within the pH range 4.5 to 9.0, when M:L=1:2. In the presence of excess ligand (M:L<=1:5), only the 1:2 complex is present, and at pH<4 paramagnetic species are detected by EPR in solution, thus indicating a reducing capacity of the ligand. Cyclic voltammetry shows that redox processes in solution are not just electron transfer, but are accompanied by chemical reactions. The pKa values and stability constants were determined both by 51V NMR spectroscopy and potentiometry. The present results have a particular interest in the understanding of the aqueous solution chemistry in aerobic conditions of bis(1,2-dimethyl-3-hydroxy-4-pyridinonato) oxovanadium(IV) complex, VO(dmpp)2, a vanadium compound with potential insulin-mimetic properties.http://www.sciencedirect.com/science/article/B6TGG-40X8DKT-3C/1/3226f220763b348a4f3d74ae0fcd0e2
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