50,848 research outputs found
Unifying type systems for mobile processes
We present a unifying framework for type systems for process calculi. The
core of the system provides an accurate correspondence between essentially
functional processes and linear logic proofs; fragments of this system
correspond to previously known connections between proofs and processes. We
show how the addition of extra logical axioms can widen the class of typeable
processes in exchange for the loss of some computational properties like
lock-freeness or termination, allowing us to see various well studied systems
(like i/o types, linearity, control) as instances of a general pattern. This
suggests unified methods for extending existing type systems with new features
while staying in a well structured environment and constitutes a step towards
the study of denotational semantics of processes using proof-theoretical
methods
Non-perturbative response: chaos versus disorder
Quantized chaotic systems are generically characterized by two energy scales:
the mean level spacing , and the bandwidth . This
implies that with respect to driving such systems have an adiabatic, a
perturbative, and a non-perturbative regimes. A "strong" quantal
non-perturbative response effect is found for {\em disordered} systems that are
described by random matrix theory models. Is there a similar effect for
quantized {\em chaotic} systems? Theoretical arguments cannot exclude the
existence of a "weak" non-perturbative response effect, but our numerics
demonstrate an unexpected degree of semiclassical correspondence.Comment: 8 pages, 2 figures, final version to be published in JP
Schr\"odinger-Feynman quantization and composition of observables in general boundary quantum field theory
We show that the Feynman path integral together with the Schr\"odinger
representation gives rise to a rigorous and functorial quantization scheme for
linear and affine field theories. Since our target framework is the general
boundary formulation, the class of field theories that can be quantized in this
way includes theories without a metric spacetime background. We also show that
this quantization scheme is equivalent to a holomorphic quantization scheme
proposed earlier and based on geometric quantization. We proceed to include
observables into the scheme, quantized also through the path integral. We show
that the quantized observables satisfy the canonical commutation relations, a
feature shared with other quantization schemes also discussed. However, in
contrast to other schemes the presented quantization also satisfies a
correspondence between the composition of classical observables through their
product and the composition of their quantized counterparts through spacetime
gluing. In the special case of quantum field theory in Minkowski space this
reproduces the operationally correct composition of observables encoded in the
time-ordered product. We show that the quantization scheme also generalizes
other features of quantum field theory such as the generating function of the
S-matrix.Comment: 47 pages, LaTeX + AMS; v2: minor corrections, references update
Ultra-short pulse compression using photonic crystal fibre
A short section of photonic crystal fibre has been used for ultra-short pulse compression. The unique optical properties of this novel medium in terms of high non-linearity and relatively small group velocity dispersion are shown to provide an ideal platform for the standard fibre pulse compression technique used directly on the nano-Joule output pulses from a commercial laser system. We report an order of magnitude reduction of the pulse width to 25 fs FWHM but predict a substantially improved performance with a dedicated fibre design. Good agreement is obtained with a simple model for the spectral broadening in the fibre
Heisenberg (and Schrödinger, and Pauli) on hidden variables
Peer reviewedPreprin
Simple geometrical interpretation of the linear character for the Zeno-line and the rectilinear diameter
The unified geometrical interpretation of the linear character of the
Zeno-line (unit compressibility line Z=1) and the rectilinear diameter is
proposed. We show that recent findings about the properties of the Zeno-line
and striking correlation with the rectilinear diameter line as well as other
empirical relations can be naturally considered as the consequences of the
projective isomorphism between the real molecular fluids and the lattice gas
(Ising) model.Comment: 7 pages, 2 figure
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