2,672 research outputs found
Majorana Fermions Signatures in Macroscopic Quantum Tunneling
Thermodynamic measurements of magnetic fluxes and I-V characteristics in
SQUIDs offer promising paths to the characterization of topological
superconducting phases. We consider the problem of macroscopic quantum
tunneling in an rf-SQUID in a topological superconducting phase. We show that
the topological order shifts the tunneling rates and quantum levels, both in
the parity conserving and fluctuating cases. The latter case is argued to
actually enhance the signatures in the slowly fluctuating limit, which is
expected to take place in the quantum regime of the circuit. In view of recent
advances, we also discuss how our results affect a -junction loop.Comment: 10 pages, 11 figure
Thermal equilibrium of two quantum Brownian particles
The influence of the environment in the thermal equilibrium properties of a
bipartite continuous variable quantum system is studied. The problem is treated
within a system-plus-reservoir approach. The considered model reproduces the
conventional Brownian motion when the two particles are far apart and induces
an effective interaction between them, depending on the choice of the spectral
function of the bath. The coupling between the system and the environment
guarantees the translational invariance of the system in the absence of an
external potential. The entanglement between the particles is measured by the
logarithmic negativity, which is shown to monotonically decrease with the
increase of the temperature. A range of finite temperatures is found in which
entanglement is still induced by the reservoir.Comment: 8 pages, 1 figur
Shallow Foundation Design through Probabilistic and Deterministic Methods
Risk and Reliability in Geotechnical Engineerin
Dynamics of topological defects in a spiral: a scenario for the spin-glass phase of cuprates
We propose that the dissipative dynamics of topological defects in a spiral
state is responsible for the transport properties in the spin-glass phase of
cuprates. Using the collective-coordinate method, we show that topological
defects are coupled to a bath of magnetic excitations. By integrating out the
bath degrees of freedom, we find that the dynamical properties of the
topological defects are dissipative. The calculated damping matrix is related
to the in-plane resistivity, which exhibits an anisotropy and linear
temperature dependence in agreement with experimental data.Comment: 4 pages, as publishe
Imaging 3D seismic velocity along the seismogenic zone of Algarve region (southern Portugal)
The present seismic tomographic study is focused around Algarve region, in South of Portugal. To locate the seismic events and find the local velocity structure of epicentral area, the P and S arrival times at 38 stations are used. The data used in this study were obtained during the Algarve campaign which worked from January/2006 to July/2007. The preliminary estimate of origin times and hypocentral coordinates are determined by the Hy- poinverse program. Linearized inversion procedure was applied to comprise the following two steps: 1) finding the minimum 1D velocity model using Velest and 2) simultaneous relocation of hypocenters and determination of local velocity structure. The velocity model we have reached is a 10 layer model which gave the lowest RMS, after several runnings of eight different velocity models that we used “a priori”. The model parameterization assumes a continuous velocity field between 4.5 km/s and 7.0 km/s until 30 km depth. The earth structure is represented in 3D by velocity at discrete points, and velocity at any intervening point is determined by linear interpolation among the surrounding eight grid points. A preliminary analysis of the resolution capabilities of the dataset, based on the Derivative Weight Sum (DWS) distribution, shows that the velocity structure is better resolved in the West part of the region between the surface to15 km. The resulting tomographic image has a prominent low-velocity anomaly that shows a maximum decrease in P-wave velocity in the first 12 kms in the studied region. We also identified the occurrence of local seismic events of reduced magnitude not catalogued, in the neighbourhood of Almodôvar (low Alentejo). The spatial distribution of epicentres defines a NE-SW direction that coincides with the strike of the mapped geological faults of the region and issued from photo-interpretation. Is still expectable to refine the seismicity of the region of Almodôvar and establish more rigorously its role in the seismotectonic picture of the region. This work is expected to produce a more detailed knowledge of the structure of the crust over the region of Algarve, being able to identify seismogenic zones, potentially generators of significant seismic events and also the identification of zones of active faults
Non-Markovian Dynamics of Quantum Discord
We evaluate the quantum discord dynamics of two qubits in independent and
common non-Markovian environments. We compare the dynamics of entanglement with
that of quantum discord. For independent reservoirs the quantum discord
vanishes only at discrete instants whereas the entanglement can disappear
during a finite time interval. For a common reservoir, quantum discord and
entanglement can behave very differently with sudden birth of the former but
not of the latter. Furthermore, in this case the quantum discord dynamics
presents sudden changes in the derivative of its time evolution which is
evidenced by the presence of kinks in its behavior at discrete instants of
time.Comment: 6 pages, 4 figure
Geoquímica das estruturas estratiformes sub-circulares da Ilha do Sal, Arquipélago de Cabo Verde
Apresenta-se o estudo de pequenas intrusões bandadas sub-circulares que ocorrem na ilha do Sal, Arquipélago de Cabo Verde. São
estruturas constituídas por alternância de bandas sub-horizontais de piroxenitos e gabros na base, a essexitos e sienitos no topo,
por vezes com intercalações de gabros com bandado fino sub-vertical. Estudos petrográficos, geoquímicos, mineraloquímicos e
petrogenéticos, integrados com os dados de campo, apontam para que estas estruturas correspondam a instrusões
sub-vulcânicas originadas por injecção de magmas de composição basanítica em pequenas câmaras magmáticas.
- …