245 research outputs found
Lorentz Symmetry and the Internal Structure of the Nucleon
To investigate the internal structure of the nucleon, it is useful to
introduce quantities that do not transform properly under Lorentz symmetry,
such as the four-momentum of the quarks in the nucleon, the amount of the
nucleon spin contributed by quark spin, etc. In this paper, we discuss to what
extent these quantities do provide Lorentz-invariant descriptions of the
nucleon structure.Comment: 6 pages, no figur
g = 2 as a Gauge Condition
Charged matter spin-1 fields enjoy a nonelectromagnetic gauge symmetry when
interacting with vacuum electromagnetism, provided their gyromagnetic ratio is
2.Comment: 5 pages, REVTeX, submitted to Phys Rev D Brief Report
Correlation functions, Bell's inequalities and the fundamental conservation laws
I derive the correlation function for a general theory of two-valued spin
variables that satisfy the fundamental conservation law of angular momentum.
The unique theory-independent correlation function is identical to the quantum
mechanical correlation function. I prove that any theory of correlations of
such discrete variables satisfying the fundamental conservation law of angular
momentum violates the Bell's inequalities. Taken together with the Bell's
theorem, this result has far reaching implications. No theory satisfying
Einstein locality, reality in the EPR-Bell sense, and the validity of the
conservation law can be constructed. Therefore, all local hidden variable
theories are incompatible with fundamental symmetries and conservation laws.
Bell's inequalities can be obeyed only by violating a conservation law. The
implications for experiments on Bell's inequalities are obvious. The result
provides new insight regarding entanglement, and its measures.Comment: LaTeX, 12pt, 11 pages, 2 figure
The electromagnetic energy-momentum tensor
We clarify the relation between canonical and metric energy-momentum tensors.
In particular, we show that a natural definition arises from Noether's Theorem
which directly leads to a symmetric and gauge invariant tensor for
electromagnetic field theories on an arbitrary space-time of any dimension
Dynamics of a self gravitating light-like matter shell: a gauge-invariant Lagrangian and Hamiltonian description
A complete Lagrangian and Hamiltonian description of the theory of
self-gravitating light-like matter shells is given in terms of
gauge-independent geometric quantities. For this purpose the notion of an
extrinsic curvature for a null-like hypersurface is discussed and the
corresponding Gauss-Codazzi equations are proved. These equations imply Bianchi
identities for spacetimes with null-like, singular curvature. Energy-momentum
tensor-density of a light-like matter shell is unambiguously defined in terms
of an invariant matter Lagrangian density. Noether identity and
Belinfante-Rosenfeld theorem for such a tensor-density are proved. Finally, the
Hamiltonian dynamics of the interacting system: ``gravity + matter'' is derived
from the total Lagrangian, the latter being an invariant scalar density.Comment: 20 pages, RevTeX4, no figure
A note on "symmetric" vielbeins in bimetric, massive, perturbative and non perturbative gravities
We consider a manifold endowed with two different vielbeins
and corresponding to two different metrics and
. Such a situation arises generically in bimetric or massive
gravity (including the recently discussed version of de Rham, Gabadadze and
Tolley), as well as in perturbative quantum gravity where one vielbein
parametrizes the background space-time and the other the dynamical degrees of
freedom. We determine the conditions under which the relation can be
imposed (or the "Deser-van Nieuwenhuizen" gauge chosen). We clarify and correct
various statements which have been made about this issue.Comment: 20 pages. Section 7, prop. 6 and 7. added. Some results made more
precis
A test generation framework for quiescent real-time systems
We present an extension of Tretmans theory and algorithm for test generation for input-output transition systems to real-time systems. Our treatment is based on an operational interpretation of the notion of quiescence in the context of real-time behaviour. This gives rise to a family of implementation relations parameterized by observation durations for quiescence. We define a nondeterministic (parameterized) test generation algorithm that generates test cases that are sound with respect to the corresponding implementation relation. Also, the test generation is exhaustive in the sense that for each non-conforming implementation a test case can be generated that detects the non-conformance
Common Causes and The Direction of Causation
Is the common cause principle merely one of a set of useful heuristics for discovering causal relations, or is it rather a piece of heavy duty metaphysics, capable of grounding the direction of causation itself? Since the principle was introduced in Reichenbach’s groundbreaking work The Direction of Time (1956), there have been a series of attempts to pursue the latter program—to take the probabilistic relationships constitutive of the principle of the common cause and use them to ground the direction of causation. These attempts have not all explicitly appealed to the principle as originally formulated; it has also appeared in the guise of independence conditions, counterfactual overdetermination, and, in the causal modelling literature, as the causal markov condition. In this paper, I identify a set of difficulties for grounding the asymmetry of causation on the principle and its descendents. The first difficulty, concerning what I call the vertical placement of causation, consists of a tension between considerations that drive towards the macroscopic scale, and considerations that drive towards the microscopic scale—the worry is that these considerations cannot both be comfortably accommodated. The second difficulty consists of a novel potential counterexample to the principle based on the familiar Einstein Podolsky Rosen (EPR) cases in quantum mechanics
Optimal Control of Quantum Dynamics : A New Theoretical Approach
A New theoretical formalism for the optimal quantum control has been
presented. The approach stems from the consideration of describing the
time-dependent quantum system in terms of the real physical observables, viz.,
the probability density rho(x,t) and the quantum current j(x,t) which is well
documented in the Bohm's hydrodynamical formulation of quantum mechanics. The
approach has been applied for manipulating the vibrational motion of HBr in its
ground electronic state under an external electric field.Comment: 4 figure
Physical theory of the twentieth century and contemporary philosophy
It has been shown that the criticism of Pauli as well as of Susskind and
Glogover may be avoided if the standard quantum-mechanical mathematical model
has been suitably extended. There is not more any reason for Einstein's
citicism, either, if in addition to some new results concerning Bell's
inequalities and Belifante's argument are taken into account. The ensemble
interpretation of quantum mechanics (or the hidden-variable theory) should be
preferred, which is also supported by the already published results of
experiments with three polarizers. Greater space in the text has been devoted
also to the discussion of epistemological problems and some philosophical
consequences.Comment: 12 page
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