16,994 research outputs found
Proof of Jacobi identity in generalized quantum dynamics
We prove that the Jacobi identity for the generalized Poisson bracket is
satisfied in the generalization of Heisenberg picture quantum mechanics
recently proposed by one of us (SLA). The identity holds for any combination of
fermionic and bosonic fields, and requires no assumptions about their mutual
commutativity.Comment: 9 pages, plain tex file, IASSNS-HEP-93/4
High transverse momentum suppression and surface effects in Cu+Cu and Au+Au collisions within the PQM model
We study parton suppression effects in heavy-ion collisions within the Parton
Quenching Model (PQM). After a brief summary of the main features of the model,
we present comparisons of calculations for the nuclear modification and the
away-side suppression factor to data in Au+Au and Cu+Cu collisions at 200 GeV.
We discuss properties of light hadron probes and their sensitivity to the
medium density within the PQM Monte Carlo framework.Comment: Comments: 6 pages, 8 figures. To appear in the proceedings of Hot
Quarks 2006: Workshop for Young Scientists on the Physics of
Ultrarelativistic Nucleus-Nucleus Collisions, Villasimius, Italy, 15-20 May
200
Towards Quantum Superpositions of a Mirror: an Exact Open Systems Analysis
We analyze the recently proposed mirror superposition experiment of Marshall,
Simon, Penrose, and Bouwmeester, assuming that the mirror's dynamics contains a
non-unitary term of the Lindblad type proportional to -[q,[q,\rho]], with q the
position operator for the center of mass of the mirror, and \rho the
statistical operator. We derive an exact formula for the fringe visibility for
this system. We discuss the consequences of our result for tests of
environmental decoherence and of collapse models. In particular, we find that
with the conventional parameters for the CSL model of state vector collapse,
maintenance of coherence is expected to within an accuracy of at least 1 part
in 10^{8}. Increasing the apparatus coupling to environmental decoherence may
lead to observable modifications of the fringe visibility, with time dependence
given by our exact result.Comment: 4 pages, RevTeX. Substantial changes mad
Symmetries of modules of differential operators
Let be the space of tensor densities of degree (or
weight) on the circle . The space of -th order linear differential operators from
to is a natural module over
, the diffeomorphism group of . We determine the
algebra of symmetries of the modules , i.e.,
the linear maps on commuting with the
-action. We also solve the same problem in the case of
straight line (instead of ) and compare the results in the
compact and non-compact cases.Comment: 29 pages, LaTeX, 4 figure
Multidimensional Inverse Scattering of Integrable Lattice Equations
We present a discrete inverse scattering transform for all ABS equations
excluding Q4. The nonlinear partial difference equations presented in the ABS
hierarchy represent a comprehensive class of scalar affine-linear lattice
equations which possess the multidimensional consistency property. Due to this
property it is natural to consider these equations living in an N-dimensional
lattice, where the solutions depend on N distinct independent variables and
associated parameters. The direct scattering procedure, which is
one-dimensional, is carried out along a staircase within this multidimensional
lattice. The solutions obtained are dependent on all N lattice variables and
parameters. We further show that the soliton solutions derived from the Cauchy
matrix approach are exactly the solutions obtained from reflectionless
potentials, and we give a short discussion on inverse scattering solutions of
some previously known lattice equations, such as the lattice KdV equation.Comment: 18 page
Implications of Weak-Interaction Space Deformation for Neutrino Mass Measurements
The negative values for the squares of both electron and muon neutrino masses
obtained in recent experiments are explained as a possible consequence of a
change in metric within the weak-interaction volume in the energy-momentum
representation. Using a model inspired by a combination of the general theory
of relativity and the theory of deformation for continuous media, it is shown
that the negative value of the square of the neutrino mass can be obtained
without violating allowed physical limits. The consequence is that the negative
value is not necessary unphysical.Comment: 12 pages, 5 figures, LaTe
Breaking quantum linearity: constraints from human perception and cosmological implications
Resolving the tension between quantum superpositions and the uniqueness of
the classical world is a major open problem. One possibility, which is
extensively explored both theoretically and experimentally, is that quantum
linearity breaks above a given scale. Theoretically, this possibility is
predicted by collapse models. They provide quantitative information on where
violations of the superposition principle become manifest. Here we show that
the lower bound on the collapse parameter lambda, coming from the analysis of
the human visual process, is ~ 7 +/- 2 orders of magnitude stronger than the
original bound, in agreement with more recent analysis. This implies that the
collapse becomes effective with systems containing ~ 10^4 - 10^5 nucleons, and
thus falls within the range of testability with present-day technology. We also
compare the spectrum of the collapsing field with those of known cosmological
fields, showing that a typical cosmological random field can yield an efficient
wave function collapse.Comment: 13 pages, LaTeX, 3 figure
Min-oscillations in Escherichia coli induced by interactions of membrane-bound proteins
During division it is of primary importance for a cell to correctly determine
the site of cleavage. The bacterium Escherichia coli divides in the center,
producing two daughter cells of equal size. Selection of the center as the
correct division site is in part achieved by the Min-proteins. They oscillate
between the two cell poles and thereby prevent division at these locations.
Here, a phenomenological description for these oscillations is presented, where
lateral interactions between proteins on the cell membrane play a key role.
Solutions to the dynamic equations are compared to experimental findings. In
particular, the temporal period of the oscillations is measured as a function
of the cell length and found to be compatible with the theoretical prediction.Comment: 17 pages, 5 figures. Submitted to Physical Biolog
The Attractor and the Quantum States
The dissipative dynamics anticipated in the proof of 't Hooft's existence
theorem -- "For any quantum system there exists at least one deterministic
model that reproduces all its dynamics after prequantization" -- is constructed
here explicitly. We propose a generalization of Liouville's classical phase
space equation, incorporating dissipation and diffusion, and demonstrate that
it describes the emergence of quantum states and their dynamics in the
Schroedinger picture. Asymptotically, there is a stable ground state and two
decoupled sets of degrees of freedom, which transform into each other under the
energy-parity symmetry of Kaplan and Sundrum. They recover the familiar Hilbert
space and its dual. Expectations of observables are shown to agree with the
Born rule, which is not imposed a priori. This attractor mechanism is
applicable in the presence of interactions, to few-body or field theories in
particular.Comment: 14 pages; based on invited talk at 4th Workshop ad memoriam of Carlo
Novero "Advances in Foundations of Quantum Mechanics and Quantum Information
with Atoms and Photons", Torino, May 2008; submitted to Int J Qu Inf
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