332 research outputs found
The Coupling of Shape Dynamics to Matter
Shape Dynamics (SD) is a theory dynamically equivalent to vacuum General
Relativity (GR), which has a different set of symmetries. It trades refoliation
invariance, present in GR, for local 3-dimensional conformal invariance. This
contribution to the Loops 11 conference addresses one of the more urgent
questions regarding the equivalence: is it possible to incorporate normal
matter in the new framework? The answer is yes, in certain regimes. We present
general criteria for coupling and apply it to a few examples.The outcome
presents bounds and conditions on scalar densities (such as the Higgs potential
and the cosmological constant) not present in GR.Comment: 4 pages. Contribution to Loops '11 conference in Madrid, to appear in
Journal of Physics: Conference Series (JPCS
Thiemann transform for gravity with matter fields
The generalised Wick transform discovered by Thiemann provides a
well-established relation between the Euclidean and Lorentzian theories of
general relativity. We extend this Thiemann transform to the Ashtekar
formulation for gravity coupled with spin-1/2 fermions, a non-Abelian
Yang-Mills field, and a scalar field. It is proved that, on functions of the
gravitational and matter phase space variables, the Thiemann transform is
equivalent to the composition of an inverse Wick rotation and a constant
complex scale transformation of all fields. This result holds as well for
functions that depend on the shift vector, the lapse function, and the Lagrange
multipliers of the Yang-Mills and gravitational Gauss constraints, provided
that the Wick rotation is implemented by means of an analytic continuation of
the lapse. In this way, the Thiemann transform is furnished with a geometric
interpretation. Finally, we confirm the expectation that the generator of the
Thiemann transform can be determined just from the spin of the fields and give
a simple explanation for this fact.Comment: LaTeX 2.09, 14 pages, no figure
Noise-tolerant Modular Neural Network System for Classifying ECG Signal
Millions of electrocardiograms (ECG) are interpreted every year, requiring specialized training for accurate interpretation. Because automated and accurate classification ECG signals will improve early diagnosis of heart condition, several neural network (NN) approaches have been proposed for classifying ECG signals. Current strategies for a critical step, the preprocessing for noise removal, are still unsatisfactory. We propose a modular NN approach based on artificial noise injection, to improve the generalization capability of the resulting model. The NN classifier initially performed a fairly accurate recognition of four types of cardiac anomalies in simulated ECG signals with minor, moderate, severe, and extreme noise, with an average accuracy of 99.2%, 95.1%, 91.4%, and 85.2% respectively. Ultimately we discriminated normal and abnormal heartbeat patterns for single lead of raw ECG signals, obtained 95.7% of overall accuracy and 99.5% of Precision. Therefore, the propose approach is a useful tool for the detection and diagnosis of cardiac abnormalities
Correlations across horizons in quantum cosmology
Different spacetime regions separated by horizons are not related to each
other. We know that this statement holds for classical spacetimes. In this
paper we carry out a canonical quantization of a Kantowski-Sachs minisuperspace
model whose classical solutions exhibit both an event horizon and a
cosmological horizon in order to check whether the above statement also holds
from the quantum gravitational point of view. Our analysis shows that in fact
this is not the case: Quantum gravitational states with support in spacetime
configurations that exclusively describe either the region between horizons or
outside them are not consistent in the sense that there exist unitary operators
describing a natural notion of evolution that connect them. In other words,
unitarity is only preserved in this quantization when dealing with the whole
spacetime and not in each region separately.Comment: 10 pages, 5 figure
Inner boundary conditions for black hole Initial Data derived from Isolated Horizons
We present a set of boundary conditions for solving the elliptic equations in
the Initial Data Problem for space-times containing a black hole, together with
a number of constraints to be satisfied by the otherwise freely specifiable
standard parameters of the Conformal Thin Sandwich formulation. These
conditions altogether are sufficient for the construction of a horizon that is
instantaneously in equilibrium in the sense of the Isolated Horizons formalism.
We then investigate the application of these conditions to the Initial Data
Problem of binary black holes and discuss the relation of our analysis with
other proposals that exist in the literature.Comment: 13 pages. Major general revision. Section V comparing with previous
approaches restructured; discussion on the lapse boundary condition extended.
Appendix with some technical details added. Version accepted for publication
in Phys.Rev.
Quantum time uncertainty in Schwarzschild-anti-de Sitter black holes
The combined action of gravity and quantum mechanics gives rise to a minimum
time uncertainty in the lowest order approximation of a perturbative scheme, in
which quantum effects are regarded as corrections to the classical spacetime
geometry. From the nonperturbative point of view, both gravity and quantum
mechanics are treated on equal footing in a description that already contains
all possible backreaction effects as those above in a nonlinear manner. In this
paper, the existence or not of such minimum time uncertainty is analyzed in the
context of Schwarzschild-anti-de Sitter black holes using the isolated horizon
formalism. We show that from a perturbative point of view, a nonzero time
uncertainty is generically present owing to the energy scale introduced by the
cosmological constant, while in a quantization scheme that includes
nonperturbatively the effects of that scale, an arbitrarily high time
resolution can be reached.Comment: 10 pages, version published in Physical Review
24-Hour Blood Pressure Variability Assessed by Average Real Variability: A Systematic Review and Meta-Analysis
Background-—Although 24-hour blood pressure (BP) variability (BPV) is predictive of cardiovascular outcomes independent of absolute BP levels, it is not regularly assessed in clinical practice. One possible limitation to routine BPV assessment is the lack of standardized methods for accurately estimating 24-hour BPV. We conducted a systematic review to assess the predictive power of reported BPV indexes to address appropriate quantification of 24-hour BPV, including the average real variability (ARV) index.
Methods and Results-—Studies chosen for review were those that presented data for 24-hour BPV in adults from meta-analysis, longitudinal or cross-sectional design, and examined BPV in terms of the following issues: (1) methods used to calculate and evaluate ARV; (2) assessment of 24-hour BPV determined using noninvasive ambulatory BP monitoring; (3) multivariate analysis adjusted for covariates, including some measure of BP; (4) association of 24-hour BPV with subclinical organ damage; and (5) the predictive value of 24-hour BPV on target organ damage and rate of cardiovascular events. Of the 19 assessed studies, 17 reported significant associations between high ARV and the presence and progression of subclinical organ damage, as well as the incidence of hard end points, such as cardiovascular events. In all these cases, ARV remained a significant independent predictor (P
Conclusions-—Current evidence suggests that ARV index adds significant prognostic information to 24-hour ambulatory BP monitoring and is a useful approach for studying the clinical value of BPV
Real-Time Implementation of qZSC for MVDC to Microgrids Link
Nowadays, power systems require new solutions to integrate renewable energies. In this paper, microgrids linked to MVDC are proposed through quasi-impedance-source converters to improve system reliability. Several prototypes are implemented using real-time platforms to analyze the system behavior, but the real-time implementation of the shoot-through state of the qZSC requires a very low time-step and sample time, which is not easy to achieve. The results obtained with these prototypes are included. Finally, a satisfactory solution is presented, implementing the power system in Typhoon HIL-402, the qZSC control in dSPACE MicroLabBox, and generating the gate signals in the FPGA included in the MicroLabBox platform. © 2022, European Association for the Development of Renewable Energy, Environment and Power Quality (EA4EPQ). All rights reserved
Asymptotically anti-de Sitter wormholes
Starting with a procedure for dealing with general asymptotic behaviors, we
construct a quantum theory for asymptotically anti-de Sitter wormholes. We
follow both the path integral formalism and the algebraic quantization program
proposed by Ashtekar. By adding suitable surface terms, the Euclidean action of
the asymptoically anti-de Sitter wormholes can be seen to be finite and gauge
invariant. This action determines an appropriate variational problem for
wormholes. We also obtain the wormhole wave functions of the gravitational
model and show that all the physical states of the quantum theory are
superpositions of wormhole states.Comment: 10 pages, RevTeX 3.0, LaTeX 2.0
Immirzi Ambiguity in the Kinematics of Quantum General Relativity
The Immirzi ambiguity arises in loop quantum gravity when geometric operators
are represented in terms of different connections that are related by means of
an extended Wick transform. We analyze the action of this transform in gravity
coupled with matter fields and discuss its analogy with the Wick rotation on
which the Thiemann transform between Euclidean and Lorentzian gravity is based.
In addition, we prove that the effect of this extended Wick transform is
equivalent to a constant scale transformation as far as the symplectic
structure and kinematical constraints are concerned. This equivalence is broken
in the dynamical evolution. Our results are applied to the discussion of the
black hole entropy in the limit of large horizon areas. We first argue that,
since the entropy calculation is performed for horizons of fixed constant area,
one might in principle choose an Immirzi parameter that depends on this
quantity. This would spoil the linearity with the area in the entropy formula.
We then show that the Immirzi parameter appears as a constant scaling in all
the steps where dynamical information plays a relevant role in the entropy
calculation. This fact, together with the kinematical equivalence of the
Immirzi ambiguity with a change of scale, is used to preclude the potential
non-linearity of the entropy on physical grounds.Comment: very minor stylistic changes, version published in Phys. Rev.
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