6,786 research outputs found
Comb entanglement in quantum spin chains
Bipartite entanglement in the ground state of a chain of quantum spins
can be quantified either by computing pairwise concurrence or by dividing the
chain into two complementary subsystems. In the latter case the smaller
subsystem is usually a single spin or a block of adjacent spins and the
entanglement differentiates between critical and non-critical regimes. Here we
extend this approach by considering a more general setting: our smaller
subsystem consists of a {\it comb} of spins, spaced sites apart.
Our results are thus not restricted to a simple `area law', but contain
non-local information, parameterized by the spacing . For the XX model we
calculate the von-Neumann entropy analytically when and
investigate its dependence on and . We find that an external magnetic
field induces an unexpected length scale for entanglement in this case.Comment: 6 pages, 4 figure
A new correlator in quantum spin chains
We propose a new correlator in one-dimensional quantum spin chains, the
Emptiness Formation Probability (EFP). This is a natural generalization
of the Emptiness Formation Probability (EFP), which is the probability that the
first spins of the chain are all aligned downwards. In the EFP we let
the spins in question be separated by sites. The usual EFP corresponds to
the special case when , and taking allows us to quantify non-local
correlations. We express the EFP for the anisotropic XY model in a
transverse magnetic field, a system with both critical and non-critical
regimes, in terms of a Toeplitz determinant. For the isotropic XY model we find
that the magnetic field induces an interesting length scale.Comment: 6 pages, 1 figur
Supersymmetric Higgs pair discovery prospects at hadron colliders
We study the potential of hadron colliders in the search for the pair
production of neutral Higgs bosons in the framework of the Minimal
Supersymmetric Standard Model. Using analytical expressions for the relevant
amplitudes, we perform a detailed signal and background analysis, working out
efficient kinematical cuts for the extraction of the signal. The important role
of squark loop contributions to the signal is emphasised. If the signal is
sufficiently enhanced by these contributions, it could even be observable at
the next run of the upgraded Tevatron collider in the near future. At the LHC
the pair production of light and heavy Higgs bosons might be detectable
simultaneously.Comment: 5 pages, hep99, 6 figures; Presented at the International Europhysics
Conference on High Energy Physics, Tampere, Finland, 15-21 July 199
Fatores que afetam o grau de diarreia em bezerros da raƧa Canchim.
Verificaram-se os efeitos de alguns fatores sobre o grau de diarreia de 245 bezerros nascidos em 1982, e de 178 bezerros nascidos em 1983, em um rebanho de gado Canchim
InfluĆŖncia da suplementaĆ§Ć£o sobre o peso Ć puberdade e as idades Ć puberdade e aos trezentos quilos de fĆŖmeas da raƧa Canchim.
O objetivo do trabalho foi avaliar a influencia da suplementaĆ§Ć£o com farelo de soja e/ou cana de aƧucar, no peso a puberdade (PP) e nas idades a puberdade (IP) e aos 300 kg de peso vivo (IT) de fĆŖmeas da raƧa Canchim
InfluĆŖncia da suplementaĆ§Ć£o alimentar sobre o desenvolvimento pos-desmama de bezerros da raƧa Canchim.
O objetivo do experimento foi avaliar o efeito da suplementaĆ§Ć£o com cana-de-aƧucar, farelo de soja e cana-de-aƧucar + farelo de soja no desenvolvimento pos-desmama de bezerras da raƧa Canchim, criadas em regime de pastagens
SubstituiĆ§Ć£o da espiga de milho desintegrada com palha e sabugo pela mandioca integral seca na alimentaĆ§Ć£o de equinos.
O objetivo de estudar a viabilidade da substituiĆ§Ć£o parcial/total da espiga de milho desintegrada ecom palha e sabugo (MDPS) pela mandioca integral (raiz + parte aĆ©rea) seca (MIS) ao sol, na alimentaĆ§Ć£o de poltras da raƧa Arabe, por meio de consumo, ganho de peso e coeficiente de digestibilidade(CD) da MS, PB, FB, e EB
Limits on Anomalous Top Couplings from Z Pole Physics
We obtain constraints on possible anomalous interactions of the top quark
with the electroweak vector bosons arising from the precision measurements at
the Z pole. In the framework of chiral Lagrangians, we
examine all effective CP-conserving operators of dimension five which induce
fermionic currents involving the top quark. We constrain the magnitudes of
these anomalous interactions by evaluating their one-loop contributions to the
Z pole physics. Our analysis shows that the operators that contribute to the
LEP observables get bounds close to the theoretical expectation for their
anomalous couplings. We also show that those which break the
custodial symmetry are more strongly bounded.Comment: expanded version, 14 pages, 1 figures adde
Efeitos de micronutrientes em capim coloniĆ£o (Panicum maximum, Jacq.) cultivado num solo de campo cerrado.
Utilizando-se de um solo de campo cerrado (Latosol Vermelho Amarelo - fase arenosa), que nunca recebeu qualquer adubaĆ§Ć£o, instalou-se este experimento em vasos, em casa de vegetaĆ§Ć£o, com a finalidade de se verificar a influencia dos micronutrientes: ManganĆŖs, molibdenio, cobre, zinco e boro, sobre o desenvolvimento do capim colonia
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