4,393 research outputs found
Chaplygin Gravitodynamics
We consider a new approach for gravity theory coupled to Chaplygin matter in
which the {\it{relativistic}} formulation of the latter is of crucial
importance. We obtain a novel form of matter with dust like density and negative pressure. We explicitly show that our results are
compatible with a relativistic generalization of the energy conservation
principle, derived here.Comment: Title changed, Revised version,N o change in conclusions, Journal
ref.: MPL A21 (2006)1511-151
Remarks on the Noncommutative Gravitational Quantum Well
A planar phase space having both position and momentum noncommutativity is
defined in a more inclusive setting than that considered elsewhere. The
dynamics of a particle in a gravitational quantum well in this space is
studied. The use of the WKB approximation and the virial theorem enable
analytic discussions on the effect of noncommutativity. Consistent results are
obtained following either commutative space or noncommutative space
descriptions. Comparison with recent experimental data with cold neutrons at
Grenoble imposes an upper bound on the noncommutative parameter. Also, our
results are compared with a recent numerical analysis of a similar problem.Comment: Latex, 17 pages, Title changed, minor modifications, 3 new references
added, To appear in Phys. Rev.
Sumoylation silences the plasma membrane leak K+ channel K2P1.
Reversible, covalent modification with small ubiquitin-related modifier proteins (SUMOs) is known to mediate nuclear import/export and activity of transcription factors. Here, the SUMO pathway is shown to operate at the plasma membrane to control ion channel function. SUMO-conjugating enzyme is seen to be resident in plasma membrane, to assemble with K2P1, and to modify K2P1 lysine 274. K2P1 had not previously shown function despite mRNA expression in heart, brain, and kidney and sequence features like other two-P loop K+ leak (K2P) pores that control activity of excitable cells. Removal of the peptide adduct by SUMO protease reveals K2P1 to be a K+-selective, pH-sensitive, openly rectifying channel regulated by reversible peptide linkage
The Mythology of Game Theory
Non-cooperative game theory is at its heart a theory of cognition, specifically a theory of how decisions are made. Game theory\u27s leverage is that we can design different payoffs, settings, player arrays, action possibilities, and information structures, and that these differences lead to different strategies, outcomes, and equilibria. It is well-known that, in experimental settings, people do not adopt the predicted strategies, outcomes, and equilibria. The standard response to this mismatch of prediction and observation is to add various psychological axioms to the game-theoretic framework. Regardless of the differing specific proposals and results, game theory uniformly makes certain cognitive assumptions that seem rarely to be acknowledged, much less interrogated. Indeed, it is not widely understood that game theory is essentially a cognitive theory. Here, we interrogate those cognitive assumptions. We do more than reject specific predictions from specific games. More broadly, we reject the underlying cognitive model implicitly assumed by game theory
Discrete versions of some Dirac type equations and plane wave solutions
A discrete version of the plane wave solution to some discrete Dirac type
equations in the spacetime algebra is established. The conditions under which a
discrete analogue of the plane wave solution satisfies the discrete Hestenes
equation are briefly discussed.Comment: 12 pages. arXiv admin note: text overlap with arXiv:1609.0459
Lagrangian generators of the Poincare gauge symmetries
We have systematically computed the generators of the symmetries arising in
Poincare gauge theory formulation of gravity, both in 2+1 and 3+1 dimensions.
This was done using a completely Lagrangian approach. The results are expected
to be valid in any dimensions, as seen through lifting the results of the 2+1
dimensional example into the 3+1 dimensional one.Comment: Latex2e, 15 pages, 1 figure; (v2) Appendix containing discussion on
applications of Lagrangian generators adde
Anonymous quantum communication
We present the first protocol for the anonymous transmission of a quantum
state that is information-theoretically secure against an active adversary,
without any assumption on the number of corrupt participants. The anonymity of
the sender and receiver is perfectly preserved, and the privacy of the quantum
state is protected except with exponentially small probability. Even though a
single corrupt participant can cause the protocol to abort, the quantum state
can only be destroyed with exponentially small probability: if the protocol
succeeds, the state is transferred to the receiver and otherwise it remains in
the hands of the sender (provided the receiver is honest).Comment: 11 pages, to appear in Proceedings of ASIACRYPT, 200
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