303,497 research outputs found
Path-integral evolution of multivariate systems with moderate noise
A non Monte Carlo path-integral algorithm that is particularly adept at
handling nonlinear Lagrangians is extended to multivariate systems. This
algorithm is particularly accurate for systems with moderate noise.Comment: 15 PostScript pages, including 7 figure
Statistical mechanics of neocortical interactions: High resolution path-integral calculation of short-term memory
We present high-resolution path-integral calculations of a previously
developed model of short-term memory in neocortex. These calculations, made
possible with supercomputer resources, supplant similar calculations made in L.
Ingber, Phys. Rev. E 49, 4652 (1994), and support coarser estimates made in L.
Ingber, Phys. Rev. A 29, 3346 (1984). We also present a current experimental
context for the relevance of these calculations using the approach of
statistical mechanics of neocortical interactions, especially in the context of
electroencephalographic data.Comment: 35 PostScript pages, including 14 figure
Dualism between Physical Frames and Time in Quantum Gravity
In this work we present a discussion of the existing links between the
procedures of endowing the quantum gravity with a real time and of including in
the theory a physical reference frame. More precisely, as first step, we
develop the canonical quantum dynamics, starting from the Einstein equations in
presence of a dust fluid and arrive to a Schroedinger evolution. Then, by
fixing the lapse function in the path integral of gravity, we get a
Schroedinger quantum dynamics, of which eigenvalues problem provides the
appearance of a dust fluid in the classical limit. The main issue of our
analysis is to claim that a theory, in which the time displacement invariance,
on a quantum level, is broken, is indistinguishable from a theory for which
this symmetry holds, but a real reference fluid is included.Comment: 9 pages, submitted to Mod. Phys. Lett. A, major replacements in
section 3 and
Codimension-2 surfaces and their Hilbert spaces: low-energy clues for holography from general covariance
We argue that the holographic principle may be hinted at already from
low-energy considerations, assuming diffeomorphism invariance, quantum
mechanics and Minkowski-like causality. We consider the states of finite
spacelike hypersurfaces in a diffeomorphism-invariant QFT. A low-energy
regularization is assumed. We note a natural dependence of the Hilbert space on
a codimension-2 boundary surface. The Hilbert product is defined dynamically,
in terms of transition amplitudes which are described by a path integral. We
show that a canonical basis is incompatible with these assumptions, which opens
the possibility for a smaller Hilbert-space dimension than canonically
expected. We argue further that this dimension may decrease with surface area
at constant volume, hinting at holographic area-proportionality. We draw
comparisons with other approaches and setups, and propose an interpretation for
the non-holographic space of graviton states at asymptotically-Minkowski null
infinity.Comment: 13 pages, 9 eps figures. Added Section VI, improved presentation.
Expanded and split the Introduction into two sections. Added Section VII.
Added reference
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