11,652 research outputs found
Probing new physics with coherent neutrino scattering off nuclei
The possibility off measuring for the first time neutrino-nuclei coherent
scattering has been recently discussed by several experimental collaborations.
It is shown that such a measurement may be very sensitive to non-standard
interactions of neutrinos with quarks and might set better constraints than
those coming from future neutrino factory experiments. We also comment on other
types of new physics tests, such as extra heavy neutral gauge bosons, where the
sensitivity to some models is slightly better than the Tevatron constraint and,
therefore, could give complementary bounds.Comment: 15 pages, 4 figures Discussion about Z prime corrected and extended.
Final version to be published in JHE
Magnetically-controlled impurities in quantum wires with strong Rashba coupling
We investigate the effect of strong spin-orbit interaction on the electronic
transport through non-magnetic impurities in one-dimensional systems. When a
perpendicular magnetic field is applied, the electron spin polarization becomes
momentum-dependent and spin-flip scattering appears, to first order in the
applied field, in addition to the usual potential scattering. We analyze a
situation in which, by tuning the Fermi level and the Rashba coupling, the
magnetic field can suppress the potential scattering. This mechanism should
give rise to a significant negative magnetoresistance in the limit of large
barriers.Comment: 4 pages, 2 figure
Sensitivity of low energy neutrino experiments to physics beyond the standard model
We study the sensitivity of future low energy neutrino experiments to extra
neutral gauge bosons, leptoquarks and R-parity breaking interactions. We focus
on future proposals to measure coherent neutrino-nuclei scattering and
neutrino-electron elastic scattering. We introduce a new comparative analysis
between these experiments and show that in different types of new physics it is
possible to obtain competitive bounds to those of present and future collider
experiments. For the cases of leptoquarks and R-parity breaking interactions we
found that the expected sensitivity for most of the future low energy
experimental setups is better than the current constraints.Comment: 21 pages, 5 figures. A more detailed analysis of systematic errors is
done. Final version to be published in PR
Fine-root production in two secondary forest sites with distinct ages in Eastern Amazon.
O objetivo deste trabalho foi avaliar a dinâmica de produção de raízes finas (diâmetro ≤ 2 mm) em duas áreas de floresta secundária com diferentes idades. A produção de raízes finas foi monitorada utilizando a técnica de ingrowth core em um sítio com 18 anos de idade (2 ha) e um outro sítio com 10 anos de idade (0,5 ha), localizados na região de Apeú, nordeste do Estado do Pará. Os sítios foram abandonados depois de sucessivos ciclos agrícolas, iniciados em 1940. A produção mensal de raízes vivas foi semelhante entre os sítios e influenciada pela sazonalidade pluviométrica, com maior produção durante a estação seca para massa e comprimento. No entanto, a mortalidade, em termos de massa, foi maior no sítio de 10 anos. A sazonalidade influenciou a mortalidade somente no sítio de 18 anos, seguindo o padrão observado para as raízes vivas. A influência sazonal sobre a mortalidade em termos de comprimento foi diferente entre os sítios, com maior mortalidade durante a estação chuvosa no sítio de 10 anos e maior mortalidade durante a estação seca no sítio de 18 anos. O comprimento radicular específico foi maior durante a estação chuvosa e influenciado pelos sítios, sendo maior no sítio de 10 anos. A produção de raízes finas não foi influenciada pela cronossequência dos sítios estudados, provavelmente porque a produção de raízes finas pode ter estabilizado nos sítios ou depende mais das condições de clima e solo. A produção, em termos de massa e comprimento, foram indicadores que geralmente mostraram o mesmo padrão
Multipartite Entanglement Signature of Quantum Phase Transitions
We derive a general relation between the non-analyticities of the ground
state energy and those of a subclass of the multipartite generalized global
entanglement (GGE) measure defined by T. R. de Oliveira et al. [Phys. Rev. A
73, 010305(R) (2006)] for many-particle systems. We show that GGE signals both
a critical point location and the order of a quantum phase transition (QPT). We
also show that GGE allows us to study the relation between multipartite
entanglement and QPTs, suggesting that multipartite but not bipartite
entanglement is favored at the critical point. Finally, using GGE we were able,
at a second order QPT, to define a diverging entanglement length (EL) in terms
of the usual correlation length. We exemplify this with the XY spin-1/2 chain
and show that the EL is half the correlation length.Comment: Published version. Incorporates correction made in erratu
Publicando mapas na Web: uso do ALOV Map.
Estudo de caso com a microbacia do Taquara Branca, Sumaré, SP. Definindo a estratégia de interação com mapas. Definindo o arquivo do projeto.bitstream/CNPTIA/9881/1/comuntec22.pdfAcesso em: 30 maio 2008
Unparticle physics and neutrino phenomenology
We have constrained unparticle interactions with neutrinos and electrons
using available data on neutrino-electron elastic scattering and the four CERN
LEP experiments data on mono photon production. We have found that, for
neutrino-electron elastic scattering, the MUNU experiment gives better
constraints than previous reported limits in the region d>1.5. The results are
compared with the current astrophysical limits, pointing out the cases where
these limits may or may not apply. We also discuss the sensitivity of future
experiments to unparticle physics. In particular, we show that the measurement
of coherent reactor neutrino scattering off nuclei could provide a good
sensitivity to the couplings of unparticle interaction with neutrinos and
quarks. We also discuss the case of future neutrino-electron experiments as
well as the International Linear Collider.Comment: 20 pages, 5 figures. Minor changes, final versio
Polaron and bipolaron transport in a charge segregated state of doped strongly correlated 2D semiconductor
The 2D lattice gas model with competing short and long range interactions is
appliedused for calculation of the incoherent charge transport in the classical
strongly-correlated charge segregated polaronic state. We show, by means of
Monte-Carlo simulations, that at high temperature the transport is dominated by
hopping of the dissociated correlated polarons, where with thetheir mobility is
inversely proportional to the temperature. At the temperatures below the
clustering transition temperature the bipolaron transport becomes dominant. The
energy barrier for the bipolaron hopping is determined by the Coulomb effects
and is found to be lower than the barrier for the single-polaron hopping. This
leads to drastically different temperature dependencies of mobilities for
polarons and bipolarons at low temperatures
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