7,052 research outputs found
Quantum Mechanical Breaking of Local GL(4) Invariance
We consider the gravitational coupling of a scalar field, in a reformulation
of General Relativity exhibiting local GL(4) invariance at the classical level.
We compute the one-loop contribution of the scalar to the quantum effective
potential of the vierbein and find that it does not have GL(4) invariance. The
minima of the effective potential occur for a vierbein which is proportional to
the unit matrix.Comment: 9 pages, plain-TeX, no figure
Mud volcanoes on Mars?
The term mud volcano is applied to a variety of landforms having in common a formation by extrusion of mud from beneath the ground. Although mud is the principal solid material that issues from a mud volcano, there are many examples where clasts up to boulder size are found, sometimes thrown high into the air during an eruption. Other characteristics of mud volcanoes (on Earth) are discussed. The possible presence of mud volcanoes, which are common and widespread on Earth, on Mars is considered
The local dayside reconnection rate for oblique interplanetary magnetic fields
We present an analysis of local properties of magnetic reconnection at the
dayside magnetopause for various interplanetary magnetic field (IMF)
orientations in global magnetospheric simulations. This has heretofore not been
practical because it is difficult to locate where reconnection occurs for
oblique IMF, but new techniques make this possible. The approach is to identify
magnetic separators, the curves separating four regions of differing magnetic
topology, which map the reconnection X-line. The electric field parallel to the
X-line is the local reconnection rate. We compare results to a simple model of
local two-dimensional asymmetric reconnection. To do so, we find the plasma
parameters that locally drive reconnection in the magnetosheath and
magnetosphere in planes perpendicular to the X-line at a large number of points
along the X-line. The global magnetohydrodynamic simulations are from the
three-dimensional Block-Adaptive, Tree Solarwind Roe-type Upwind Scheme
(BATS-R-US) code with a uniform resistivity, although the techniques described
here are extensible to any global magnetospheric simulation model. We find that
the predicted local reconnection rates scale well with the measured values for
all simulations, being nearly exact for due southward IMF. However, the
absolute predictions differ by an undetermined constant of proportionality,
whose magnitude increases as the IMF clock angle changes from southward to
northward. We also show similar scaling agreement in a simulation with oblique
southward IMF and a dipole tilt. The present results will be an important
component of a full understanding of the local and global properties of dayside
reconnection.Comment: 12 pages, 7 figures, 1 table, Submitted to Journal Geophysical
Research Space Physics February 12, 2016; Revised April 28, 201
Key point selection and clustering of swimmer coordination through Sparse Fisher-EM
To answer the existence of optimal swimmer learning/teaching strategies, this
work introduces a two-level clustering in order to analyze temporal dynamics of
motor learning in breaststroke swimming. Each level have been performed through
Sparse Fisher-EM, a unsupervised framework which can be applied efficiently on
large and correlated datasets. The induced sparsity selects key points of the
coordination phase without any prior knowledge.Comment: Presented at ECML/PKDD 2013 Workshop on Machine Learning and Data
Mining for Sports Analytics (MLSA2013
Self correction requires Energy Barrier for Abelian quantum doubles
We rigorously establish an Arrhenius law for the mixing time of quantum
doubles based on any Abelian group . We have made the concept of
the energy barrier therein mathematically well-defined, it is related to the
minimum energy cost the environment has to provide to the system in order to
produce a generalized Pauli error, maximized for any generalized Pauli errors,
not only logical operators. We evaluate this generalized energy barrier in
Abelian quantum double models and find it to be a constant independent of
system size. Thus, we rule out the possibility of entropic protection for this
broad group of models.Comment: 18 pages, 6 figure
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