10,201 research outputs found
Geometry, stochastic calculus and quantum fields in a non-commutative space-time
The algebras of non-relativistic and of classical mechanics are unstable
algebraic structures. Their deformation towards stable structures leads,
respectively, to relativity and to quantum mechanics. Likewise, the combined
relativistic quantum mechanics algebra is also unstable. Its stabilization
requires the non-commutativity of the space-time coordinates and the existence
of a fundamental length constant. The new relativistic quantum mechanics
algebra has important consequences on the geometry of space-time, on quantum
stochastic calculus and on the construction of quantum fields. Some of these
effects are studied in this paper.Comment: 36 pages Latex, 1 eps figur
Avalanche Collapse of Interdependent Network
We reveal the nature of the avalanche collapse of the giant viable component
in multiplex networks under perturbations such as random damage. Specifically,
we identify latent critical clusters associated with the avalanches of random
damage. Divergence of their mean size signals the approach to the hybrid phase
transition from one side, while there are no critical precursors on the other
side. We find that this discontinuous transition occurs in scale-free multiplex
networks whenever the mean degree of at least one of the interdependent
networks does not diverge.Comment: 4 pages, 5 figure
Soft singularity and the fundamental length
It is shown that some regular solutions in 5D Kaluza-Klein gravity may have
interesting properties if one from the parameters is in the Planck region. In
this case the Kretschman metric invariant runs up to a maximal reachable value
in nature, i.e. practically the metric becomes singular. This observation
allows us to suppose that in this situation the problems with such soft
singularity will be much easier resolved in the future quantum gravity then by
the situation with the ordinary hard singularity (Reissner-Nordstr\"om
singularity, for example). It is supposed that the analogous consideration can
be applied for the avoiding the hard singularities connected with the gauge
charges.Comment: 5 page
Short-time Dynamics of Percolation Observables
We consider the critical short-time evolution of magnetic and
droplet-percolation order parameters for the Ising model in two and three
dimensions, through Monte-Carlo simulations with the (local) heat-bath method.
We find qualitatively different dynamic behaviors for the two types of order
parameters. More precisely, we find that the percolation order parameter does
not have a power-law behavior as encountered for the magnetization, but
develops a scale (related to the relaxation time to equilibrium) in the
Monte-Carlo time. We argue that this difference is due to the difficulty in
forming large clusters at the early stages of the evolution. Our results show
that, although the descriptions in terms of magnetic and percolation order
parameters may be equivalent in the equilibrium regime, greater care must be
taken to interprete percolation observables at short times. In particular, this
concerns the attempts to describe the dynamics of the deconfinement phase
transition in QCD using cluster observables.Comment: 5 pages, 4 figure
Strong spin-photon coupling in silicon
We report the strong coupling of a single electron spin and a single
microwave photon. The electron spin is trapped in a silicon double quantum dot
and the microwave photon is stored in an on-chip high-impedance superconducting
resonator. The electric field component of the cavity photon couples directly
to the charge dipole of the electron in the double dot, and indirectly to the
electron spin, through a strong local magnetic field gradient from a nearby
micromagnet. This result opens the way to the realization of large networks of
quantum dot based spin qubit registers, removing a major roadblock to scalable
quantum computing with spin qubits
Transversely projective foliations on surfaces: existence of normal forms and prescription of the monodromy
We introduce a notion of normal form for transversely projective structures
of singular foliations on complex manifolds. Our first main result says that
this normal form exists and is unique when ambient space is two-dimensional.
From this result one obtains a natural way to produce invariants for
transversely projective foliations on surfaces. Our second main result says
that on projective surfaces one can construct singular transversely projective
foliations with prescribed monodromy
Estimativa de custo de produção de soja, nos sistemas plantio direto e convencional, safra 1999/2000.
bitstream/item/24905/1/Cot19992.pd
Estimativa de custo de produção de algodão, no sistema plantio convencional, safra 1999/2000.
bitstream/item/39711/1/COT-06-1999.pd
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