15,052 research outputs found
Shear-stress controlled dynamics of nematic complex fluids
Based on a mesoscopic theory we investigate the non-equilibrium dynamics of a
sheared nematic liquid, with the control parameter being the shear stress
(rather than the usual shear rate, ). To
this end we supplement the equations of motion for the orientational order
parameters by an equation for , which then becomes time-dependent.
Shearing the system from an isotropic state, the stress- controlled flow
properties turn out to be essentially identical to those at fixed .
Pronounced differences when the equilibrium state is nematic. Here, shearing at
controlled yields several non-equilibrium transitions between
different dynamic states, including chaotic regimes. The corresponding
stress-controlled system has only one transition from a regular periodic into a
stationary (shear-aligned) state. The position of this transition in the
- plane turns out to be tunable by the delay
time entering our control scheme for . Moreover, a sudden
change of the control method can {\it stabilize} the chaotic states appearing
at fixed .Comment: 10 pages, 11 figure
Irrelevance of Bell's Theorem for experiments involving correlations in space and time: a specific loophole-free computer-example
John Bell is generally credited to have accomplished the remarkable "proof"
that any theory of physics, which is both Einstein-local and "realistic"
(counterfactually definite), results in a strong upper bound to the
correlations that are measured in space and time. He thus predicts that
Einstein-Podolsky-Rosen experiments cannot violate Bell- type inequalities. We
present a counterexample to this claim, based on discrete-event computer
simulations. Our model-results fully agree with the predictions of quantum
theory for Einstein-Podolsky-Rosen-Bohm experiments and are free of the
detection- or a coincidence-loophole
Extended Analysis of Gravitomagnetic Fields in Rotating Superconductors and Superfluids
Applying the Ginzburg-Landau theory including frame dragging effects to the
case of a rotating superconductor, we were able to express the absolute value
of the gravitomagnetic field involved to explain the Cooper pair mass anomaly
previously reported by Tate. Although our analysis predicts large
gravitomagnetic fields originated by superconductive gyroscopes, those should
not affect the measurement of the Earth gravitomagnetic field by the Gravity
Probe-B satellite. However, the hypothesis might be well suited to explain a
mechanical momentum exchange phenomena reported for superfluid helium. As a
possible explanation for those abnormally large gravitomagnetic fields in
quantum materials, the reduced speed of light (and gravity) that was found in
the case of Bose-Einstein condensates is analysed
Counterfactual Definiteness and Bell's Inequality
Counterfactual definiteness must be used as at least one of the postulates or
axioms that are necessary to derive Bell-type inequalities. It is considered by
many to be a postulate that is not only commensurate with classical physics (as
for example Einstein's special relativity), but also separates and
distinguishes classical physics from quantum mechanics. It is the purpose of
this paper to show that Bell's choice of mathematical functions and independent
variables implicitly includes counterfactual definiteness and reduces the
generality of the physics of Bell-type theories so significantly that no
meaningful comparison of these theories with actual Einstein-Podolsky-Rosen
experiments can be made
Reply to the Comment by A.J. Leggett and Anupam Garg
In their comment[1] on our Letter [arXiv:0907.0767], Leggett and Garg claim
that they have introduced in their original paper (LG1) a dependence on
measurement times. They also claim that Eqs.(HMDR1) and (LG2a) can therefore
not be linked in such a way that the arguments of [arXiv:0907.0767] can be
transcribed. However, (LG1) distinguishes only three time differences, and all
experimental results corresponding to the same time differences are identically
labeled and therefore treated as mathematically identical. We therefore cannot
agree with the argumentation of Leggett and Garg: except for a change of
nomenclature Eqs.(HMDR1) and (LG2a) are the same. A more extensive discussion
of this point can be found in [arXiv:0901.2546].Comment: Published version with minor correction
Hidden assumptions in the derivation of the Theorem of Bell
John Bell's inequalities have already been considered by Boole in 1862. Boole
established a one-to-one correspondence between experimental outcomes and
mathematical abstractions of his probability theory. His abstractions are
two-valued functions that permit the logical operations AND, OR and NOT and are
the elements of an algebra. Violation of the inequalities indicated to Boole an
inconsistency of definition of the abstractions and/or the necessity to revise
the algebra. It is demonstrated in this paper, that a violation of Bell's
inequality by Einstein-Podolsky-Rosen type of experiments can be explained by
Boole's ideas. Violations of Bell's inequality also call for a revision of the
mathematical abstractions and corresponding algebra. It will be shown that this
particular view of Bell's inequalities points toward an incompleteness of
quantum mechanics, rather than to any superluminal propagation or influences at
a distance
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