1,381 research outputs found
Disseminated sulphide mineralisation at Garbh Achadh, Argyllshire, Scotland
A brief investigation of low-grade copper mineralisation associated
with a small, talc-alkaline porphyry intrusion of Caledonian age is
described.
Geological mapping has delineated a small stock of biotite-feldspar
2
porphyry, 0.25 km in area, intruded into a sequence of Dalradian schists
and quartzites with inter-bedded epidiorites. Disseminated sulphides occur
within the porphyry and the hornfelsed epidiorite but do not normally
, exceed 3% of the rock by volume. Assays of both rock types obtained maximum
levels of 0.24% Cu. Hydrothermal alteration is prominent within the
porphyry, with the widespread development of sericite and kaolinite.
Subsequent faulting apparently exerted some control on the present limits
of alteration and mineralisation. Several small strata-bound lenses of
massive sulphide within the metasediments were recorded but were not
investigated in detail.
Geochemical rock-sampling delineated a strong arcuate copper anomaly
over the northern epidiorite/porphyry contact and a more subdued anomaly
along the southern faulted contact. Molybdenum shows a similar distribution
but is more closely confined to the porphyry. Overburden sampling
demonstrated that little or no metal dispersion occurred within the overlying
till, and stream sediment sampling of the catchment area showed that
concentrations of copper decrease to background levels within 1 km of the
intrusion. 1
Induced polarisation (IP) surveys produced a clearly defined grouping
of chargeability anomalies around the edges of the porphyry stock but these
showed no increase in magnitude at depth. Above background chargeability
values recorded over the centre of the intrusion increase markedly towards
the margins , possibly reflecting a pyritic halo. Most resistivity 'lows' coincide with fault zones and the results of a total intensity magnetometer
1
survey showed that, while most magnetic anomalies occur over epidiorites,
I
significant anomalies are also produced in the vicinity of fault zones.
The results of the geological, petrographic, geochemical and
I
geophysical studies demonstrate the presence of several features
: characteristic of 'porphyry copper style' mineralisation but the small
1
surface area and low grade of the deposit, combined with a lack of
encouraging geophysical responses at depth, suggest that there is little
II chance of discovering an economic orebody by exploratory drilling
Decoherence of entangled kaons and its connection to entanglement measures
We study the time evolution of the entangled kaon system by considering the
Liouville - von Neumann equation with an additional term which allows for
decoherence. We choose as generators of decoherence the projectors to the
2-particle eigenstates of the Hamiltonian. Then we compare this model with the
data of the CPLEAR experiment and find in this way an upper bound on the
strength of the decoherence. We also relate to an effective
decoherence parameter considered previously in literature. Finally we
discuss our model in the light of different measures of entanglement, i.e. the
von Neumann entropy , the entanglement of formation and the concurrence
, and we relate the decoherence parameter to the loss of
entanglement: .Comment: comments and references added, 18 pages, 1 figur
Dissipation in a 2-dimensional Hilbert space: Various forms of complete positivity
We consider the time evolution of the density matrix in a
2-dimensional complex Hilbert space. We allow for dissipation by adding to the
von Neumann equation a term , which is of Lindblad type in order to
assure complete positivity of the time evolution. We present five equivalent
forms of . In particular, we connect the familiar dissipation matrix
with a geometric version of , where consists of a positive sum
of projectors onto planes in . We also study the minimal number
of Lindblad terms needed to describe the most general case of . All
proofs are worked out comprehensively, as they present at the same time a
practical procedure how to determine explicitly the different forms of
. Finally, we perform a general discussion of the asymptotic behaviour
of the density matrix and we relate the two types of asymptotic
behaviour with our geometric version of .Comment: 11 pages, LaTeX, no figures. Further aspects of complete positivity
worked out and references added; version accepted for publication in Phys.
Lett.
Colliders and Cosmology
Dark matter in variations of constrained minimal supersymmetric standard
models will be discussed. Particular attention will be given to the comparison
between accelerator and direct detection constraints.Comment: Submitted for the SUSY07 proceedings, 15 pages, LaTex, 26 eps figure
A river model of space
Within the theory of general relativity gravitational phenomena are usually
attributed to the curvature of four-dimensional spacetime. In this context we
are often confronted with the question of how the concept of ordinary physical
three-dimensional space fits into this picture. In this work we present a
simple and intuitive model of space for both the Schwarzschild spacetime and
the de Sitter spacetime in which physical space is defined as a specified set
of freely moving reference particles. Using a combination of orthonormal basis
fields and the usual formalism in a coordinate basis we calculate the physical
velocity field of these reference particles. Thus we obtain a vivid description
of space in which space behaves like a river flowing radially toward the
singularity in the Schwarzschild spacetime and radially toward infinity in the
de Sitter spacetime. We also consider the effect of the river of space upon
light rays and material particles and show that the river model of space
provides an intuitive explanation for the behavior of light and particles at
and beyond the event horizons associated with these spacetimes.Comment: 22 pages, 5 figure
Friedmann Robertson-Walker model in generalised metric space-time with weak anisotropy
A generalized model of space-time is given, taking into consideration the
anisotropic structure of fields which are depended on the position and the
direction (velocity).In this framework a generalized FRW-metric the
Raychaudhouri and Friedmann equations are studied.A long range vector field of
cosmological origin is considered in relation to the physical geometry of
space-time in which Cartan connection has a fundamental role.The generalised
Friedmann equations are produced including anisotropic terms.The variation of
anisotropy is expressed in terms of the Cartan torsion tensor of the
Finslerian space-time.A possible estimation of the anisotropic parameter
can be achieved with the aid of the de-Sitter model of the empty flat universe
with weak anisotropy. Finally a physical generalisation for the model of
inflation is also studied.Comment: 21 pages- to appear in GR
New laser technology to determine present weather parameters
Present weather sensors are becoming increasingly important as a means to
augment networks of automated weather stations and extend the capability
of manned observations. The classification of hydrometeors is one of the
principal tasks that is addressed by present weather sensors. In this paper,
we discuss a new laser-based technology for this purpose. The system
improves upon current precipitation monitors by using a derivative of phase
Doppler anemometry techniques to accurately determine particle speed and
size. The instrument is also capable of distinguishing between liquid
droplets and solid polycrystalline hydrometeors and can be used to estimate
visibility. The incorporation of this technology into a meteorological station
with other sensors, such as temperature and relative humidity probes, leads
to the accurate classification of particle type. The example data shown are
taken from tests in Leicestershire, England and Utah, USA and show the
differences between solid and liquid precipitation events
Gravitational field around a screwed superconducting cosmic string in scalar-tensor theories
We obtain the solution that corresponds to a screwed superconducting cosmic
string (SSCS) in the framework of a general scalar-tensor theory including
torsion. We investigate the metric of the SSCS in Brans-Dicke theory with
torsion and analyze the case without torsion. We show that in the case with
torsion the space-time background presents other properties different from that
in which torsion is absent. When the spin vanish, this torsion is a
-gradient and then it propagates outside of the string. We investigate
the effect of torsion on the gravitational force and on the geodesics of a
test-particle moving around the SSCS. The accretion of matter by wakes
formation when a SSCS moves with speed is investigated. We compare our
results with those obtained for cosmic strings in the framework of
scalar-tensor theory.Comment: 22 pages, LaTeX, presented at the "XXII - Encontro Nacional de Fisica
de Particulas e Campos", Sao Lourenco, MG, Brazi
Monte Carlo Methods for Rough Free Energy Landscapes: Population Annealing and Parallel Tempering
Parallel tempering and population annealing are both effective methods for
simulating equilibrium systems with rough free energy landscapes. Parallel
tempering, also known as replica exchange Monte Carlo, is a Markov chain Monte
Carlo method while population annealing is a sequential Monte Carlo method.
Both methods overcome the exponential slowing associated with high free energy
barriers. The convergence properties and efficiency of the two methods are
compared. For large systems, population annealing initially converges to
equilibrium more rapidly than parallel tempering for the same amount of
computational work. However, parallel tempering converges exponentially and
population annealing inversely in the computational work so that ultimately
parallel tempering approaches equilibrium more rapidly than population
annealing.Comment: 10 pages, 3 figure
On the distances between entangled pseudoscalar mesons states
Entangled states of pseudoscalar mesons represent a very interesting tool for
studying foundations of quantum mechanics, e.g. for testing Bell inequalities.
Recently, they also emerged as a test bench for quantum information protocols.
On the other hand, from a quantum information point of view, the
characterization of the distance between two quantum states is a topic of the
utmost importance. In this letter, with the purpose of providing a useful tool
for further investigations, we address the problem of which distance allows a
better discrimination between density matrices appearing in pseudoscalar
phenomenology
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