6,966 research outputs found
Generation of field mediated three qubit entangled state shared by Alice and Bob
A scheme to generate shared tripartite entangled states, with two-trapped
atoms in a cavity held by Alice (qubits A1 and A2) entangled to a single
trapped atom in a remote lab owned by Bob (B), is proposed. The entanglement is
generated through interaction of trapped atoms with two mode squeezed light
shared by the two cavities. The proposed scheme is an extension of the proposal
of ref. [W. Son, M. S. Kim, J. Lee, and D. Ahn, J. Mod. Opt. 49, 1739 (2002)],
where the possibility of entangling two remote qubits using a bipartite
continuous variable state was examined. While the global negativity detects the
free entanglement of the three atom mixed state, the bound entanglement is
detected by the negativity calculated from pure state decomposition of the
state operator. The partial negativities calculated by selective partial
transposition of the three atom mixed state detect the pairwise entanglement of
qubit pairs A1B, A2B, and A1A2. The entanglement of three atoms is found to be
W-like, no GHZ like quantum correlations being generated.Comment: 14 pages, 06 figures, section IV revised, Other minor changes to
improve readabilit
Quantum Singularities Around a Global Monopole
The behavior of a massive scalar particle on the spacetime surrounding a
monopole is studied from a quantum mechanical point of view. All the boundary
conditions necessary to turn into self-adjoint the spatial portion of the wave
operator are found and their importance to the quantum interpretation of
singularities is emphasized.Comment: 5 pages, revte
Study of the degradation of reinforced concrete structures exposed to attack by sulfates
As estruturas de betão armado quando sujeitas a ambientes agressivos tendem a perder capacidade de proteção das armaduras nelas inseridas. É conhecido que, a proteção das armaduras está associada ao PH do betão que as envolve, e cujo valor tende a diminuir na presença de sulfatos que contribuem para a descalcificação do betão. Quando o PH desce para níveis inferiores a 9, ficam criadas as condições para a dissolução da pelicula de proteção passiva das armaduras. O presente trabalho compara o comportamento de estruturas de betão armado com quatro tipos distintos de armaduras (aço macio, revestido, galvanizado e proteção catódica) exposta ao ataque por sulfatos. Recorreu-se a sondas eletroquímicas embebidas no betão para a monitorização da condutividade do betão envolvente, do potencial de corrosão do aço e da velocidade de corrosão do aço com recurso ao método da resistência à polarização linear
Lepton Flavor Violation and Collider Searches in a Type I + II Seesaw Model
Neutrino are massless in the Standard Model. The most popular mechanism to
generate neutrino masses are the type I and type II seesaw, where right-handed
neutrinos and a scalar triplet are augmented to the Standard Model,
respectively. In this work, we discuss a model where a type I + II seesaw
mechanism naturally arises via spontaneous symmetry breaking of an enlarged
gauge group. Lepton flavor violation is a common feature in such setup and for
this reason, we compute the model contribution to the
and decays. Moreover, we explore the connection between
the neutrino mass ordering and lepton flavor violation in perspective with the
LHC, HL-LHC and HE-LHC sensitivities to the doubly charged scalar stemming from
the Higgs triplet. Our results explicitly show the importance of searching for
signs of lepton flavor violation in collider and muon decays. The conclusion
about which probe yields stronger bounds depends strongly on the mass ordering
adopted, the absolute neutrino masses and which much decay one considers. In
the 1-5 TeV mass region of the doubly charged scalar, lepton flavor violation
experiments and colliders offer orthogonal and complementary probes. Thus if a
signal is observed in one of the two new physics searches, the other will be
able to assess whether it stems from a seesaw framework.Comment: 41 pages, 1 figure, 2 table
Water-like hierarchy of anomalies in a continuous spherical shouldered potential
We investigate by molecular dynamics simulations a continuous isotropic
core-softened potential with attractive well in three dimensions, introduced by
Franzese [cond-mat/0703681, to appear on Journal of Molecular Liquids], that
displays liquid-liquid coexistence with a critical point and water-like density
anomaly. Here we find diffusion and structural anomalies. These anomalies occur
with the same hierarchy that characterizes water. Yet our analysis shows
differences with respect to the water case. Therefore, many of the anomalous
features of water could be present in isotropic systems with soft-core
attractive potentials, such as colloids or liquid metals, consistent with
recent experiments showing polyamorphism in metallic glasses.Comment: 27 pages, 9 figures. to appear in J. Chem. Phy
Quantum singularities in FRW universe revisited
The components of the Riemann tensor in the tetrad basis are quantized and,
through the Einstein equation, we find the local expectation value in the
ontological interpretation of quantum mechanics of the energy density and
pressure of a perfect fluid with equation of state in the
flat Friedmann-Robertson-Walker quantum cosmological model. The quantum
behavior of the equation of state and energy conditions are then studied and it
is shown that the later is violated since the singularity is removed with the
introduction of quantum cosmology, but in the classical limit both the equation
of state and the energy conditions behave as in the classical model. We also
calculate the expectation value of the scale factor for several wave packets in
the many-worlds interpretation in order to show the independence of the non
singular character of the quantum cosmological model with respect to the wave
packet representing the wave function of the Universe. It is also shown that,
with the introduction of non-normalizable wave packets, solutions of the
Wheeler-DeWitt equation, the singular character of the scale factor, can be
recovered in the ontological interpretation.Comment: 15 pages, revtex, accepted for publication in PR
Spatial and temporal variability of precipitation and drought in Portugal
The spatial variability of precipitation and drought are investigated for Portugal using monthly precipitation from 74 stations and minimum and maximum temperature from 27 stations, covering the common period of 1941–2006. Seasonal precipitation and the corresponding percentages in the year, as well as the precipitation concentration index (PCI), was computed for all 74 stations and then used as an input matrix for an R-mode principal component analysis to identify the precipitation patterns. The standardized precipitation index at 3 and 12 month time scales were computed for all stations, whereas the Palmer Drought Severity Index (PDSI) and the modified PDSI for Mediterranean conditions (MedPDSI) were computed for the stations with temperature data. The spatial patterns of drought over Portugal were identified by applying the S-mode principal component analysis coupled with varimax rotation to the drought indices matrices. The result revealed two distinct sub-regions in the country relative to both precipitation regimes and drought variability. The analysis of time variability of the PC scores of all drought indices allowed verifying that there is no linear trend indicating drought aggravation or decrease. In addition, the analysis shows that results for SPI-3, SPI-12, PDSI and MedPDSI are coherent among them
Avaliação das propriedades mecânicas da madeira in situ por ensaios em mesoprovetes
Uma das principais dificuldades da avaliação do estado de segurança de estruturas de
madeira existentes é a determinação das propriedades mecânicas a utilizar para efeitos de
cálculo. Os procedimentos habituais de estabelecimento das propriedades mecânicas com
base no estabelecimento de classes de resistência por avaliação visual validada com ensaios
não-destrutivos conduzem a resultados muito conservativos. No presente trabalho será
apresentado um método semi-destrutivo que avalia a resistência à tracção da madeira
através de amostras recolhidas do elemento estrutural, sendo estabelecidas relações entre
resultados análogos de mesoprovetes e provetes normalizados para peças de pinho bravo
(Pinus pinaster Ait.) e castanho nacional (Castanea sativa Mill.)
Testing the Flyby Anomaly with the GNSS Constellation
We propose the concept of a space mission to probe the so called flyby
anomaly, an unexpected velocity change experienced by some deep-space probes
using earth gravity assists. The key feature of this proposal is the use of
GNSS systems to obtain an increased accuracy in the tracking of the approaching
spacecraft, mainly near the perigee. Two low-cost options are also discussed to
further test this anomaly: an add-on to an existing spacecraft and a dedicated
mission.Comment: 8 pages, 1 figure, 4 table
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