70 research outputs found
Does quantum mechanics tell an atomistic spacetime?
The canonical answer to the question posed is "Yes." -- tacitly assuming that
quantum theory and the concept of spacetime are to be unified by `quantizing' a
theory of gravitation. Yet, instead, one may ponder: Could quantum mechanics
arise as a coarse-grained reflection of the atomistic nature of spacetime? --
We speculate that this may indeed be the case. We recall the similarity between
evolution of classical and quantum mechanical ensembles, according to Liouville
and von Neumann equation, respectively. The classical and quantum mechanical
equations are indistinguishable for objects which are free or subject to
spatially constant but possibly time dependent, or harmonic forces, if
represented appropriately. This result suggests a way to incorporate anharmonic
interactions, including fluctuations which are tentatively related to the
underlying discreteness of spacetime. Being linear and local at the quantum
mechanical level, the model offers a decoherence and natural localization
mechanism. However, the relation to primordial deterministic degrees of freedom
is nonlocal.Comment: Based on invited talks at Fourth International Workshop DICE2008,
held at Castello Pasquini / Castiglioncello, Italy, 22-26 September 2008 and
at DISCRETE'08 - Symposium on Prospects in the Physics of Discrete
Symmetries, held at IFIC, Valencia, Spain, 11-16 December 2008 - to appear in
respective volumes of Journal of Physics: Conference Serie
Introduction to light cone field theory and high energy scattering
In this set of four lectures, we provide an elementary introduction to light
cone field theory and some of its applications in high energy scattering.Comment: 28 pages, LaTeX, invited lectures at Cape Town summer school in
theoretical physic
Brane-induced Skyrmion on S^3: baryonic matter in holographic QCD
We study baryonic matter in holographic QCD with D4/D8/\bar{D8} multi-D brane
system in type IIA superstring theory. The baryon is described as the
"brane-induced Skyrmion", which is a topologically non-trivial chiral soliton
in the four-dimensional meson effective action induced by holographic QCD. We
employ the "truncated-resonance model" approach for the baryon analysis,
including pion and \rho meson fields below the ultraviolet cutoff scale M_KK
\sim 1GeV, to keep the holographic duality with QCD. We describe the baryonic
matter in large N_c as single brane-induced Skyrmion on the three-dimensional
closed manifold S^3 with finite radius R. The interactions between baryons are
simulated by the curvature of the closed manifold S^3, and the decrease of the
size of S^3 represents the increase of the total baryon-number density in the
medium in this modeling. We investigate the energy density, the field
configuration, the mass and the root-mean-square radius of single baryon on S^3
as the function of its radius R. We find a new picture of "pion dominance" near
the critical density in the baryonic matter, where all the (axial) vector meson
fields disappear and only the pion field survive. We also find the "swelling"
phenomena of the baryons as the precursor of the deconfinement, and propose the
mechanism of the swelling in general context of QCD. The properties of the
deconfinement and the chiral symmetry restoration in the baryonic matter are
examined by taking the proper order parameters. We also compare our
truncated-resonance model with another "instanton" description of the baryon in
holographic QCD, considering the role of cutoff scale M_KK.Comment: 25 pages, 12 figure
Time-dependent quantum scattering in 2+1 dimensional gravity
The propagation of a localized wave packet in the conical space-time created
by a pointlike massive source in 2+1 dimensional gravity is analyzed. The
scattering amplitude is determined and shown to be finite along the classical
scattering directions due to interference between the scattered and the
transmitted wave functions. The analogy with diffraction theory is emphasized.Comment: 15 pages in LaTeX with 3 PostScript figure
Body Fixed Frame, Rigid Gauge Rotations and Large N Random Fields in QCD
The "body fixed frame" with respect to local gauge transformations is
introduced. Rigid gauge "rotations" in QCD and their \Sch equation are studied
for static and dynamic quarks. Possible choices of the rigid gauge field
configuration corresponding to a nonvanishing static colormagnetic field in the
"body fixed" frame are discussed. A gauge invariant variational equation is
derived in this frame. For large number N of colors the rigid gauge field
configuration is regarded as random with maximally random probability
distribution under constraints on macroscopic--like quantities. For the uniform
magnetic field the joint probability distribution of the field components is
determined by maximizing the appropriate entropy under the area law constraint
for the Wilson loop. In the quark sector the gauge invariance requires the
rigid gauge field configuration to appear not only as a background but also as
inducing an instantaneous quark-quark interaction. Both are random in the large
N limit.Comment: 29 pages LATEX, Weizmann Institute preprint WIS-93/40/Apr -P
Color confinement and dual superconductivity in unquenched QCD
We report on evidence from lattice simulations that confinement is produced
by dual superconductivity of the vacuum in full QCD as in quenched QCD.
Preliminary information is obtained on the order of the deconfining phase
transition.Comment: 4 pages, to appear in the Proceedings of Quark Matter 02 - The XVI
International Conference on Ultrarelativistic Nucleus-Nucleus Collision
Exact propagators on the lattice with applications to diffractive effects
The propagator of the discrete Schr\"odinger equation is computed and its
properties are revealed through a Feynman path summation in discrete space.
Initial data problems such as diffraction in discrete space and continuous time
are studied analytically by the application of the new propagator. In the
second part of this paper, the analogy between time propagation and 2D
scattering by 1D obstacles is explored. New results are given in the context of
diffraction by edges within a periodic medium. A connection with tight-binding
arrays and photonic crystals is indicated.Comment: Final version with two appendices. Published in J. Phys. A: Math.
Theo
p-Branes from Generalized Yang-Mills Theory
We consider the reduced, quenched version of a generalized Yang-Mills action
in 4k-dimensional spacetime. This is a new kind of matrix theory which is
mapped through the Weyl-Wigner-Moyal correspondence into a field theory over a
non-commutative phase space. We show that the ``classical'' limit of this field
theory is encoded into the effective action of an open, (4k-1)-dimensional,
bulk brane enclosed by a dynamical, Chern-Simons type, (4k-2)-dimensional,
boundary brane. The bulk action is a pure volume term, while the boundary
action carries all the dynamical degrees of freedom.Comment: 8 pages, LaTeX 2e, no figure
Thermally activated energy and critical magnetic fields of SmFeAsOF
Thermally activated flux flow and vortex glass transition of recently
discovered SmFeAsOF superconductor are studied in magnetic
fields up to 9.0 T. The thermally activated energy is analyzed in two analytic
methods, of which one is conventional and generally used, while the other is
closer to the theoretical description. The thermally activated energy values
determined from both methods are discussed and compared. In addition, several
critical magnetic fields determined from resistivity measurements are presented
and discussed.Comment: Accepted by Superconductor Science and Technolog. 5 page, 4 figure
Standstill Electric Charge Generates Magnetostatic Field Under Born-Infeld Electrodynamics
The Abelian Born-Infeld classical non-linear electrodynamic has been used to
investigate the electric and magnetostatic fields generated by a point-like
electrical charge at rest in an inertial frame. The results show a rich
internal structure for the charge. Analytical solutions have also been found.
Such findings have been interpreted in terms of vacuum polarization and
magnetic-like charges produced by the very high strengths of the electric field
considered. Apparently non-linearity is to be accounted for the emergence of an
anomalous magnetostatic field suggesting a possible connection to that created
by a magnetic dipole composed of two mognetic charges with opposite signals.
Consistently in situations where the Born-Infeld field strength parameter is
free to become infinite, Maxwell`s regime takes over, the magnetic sector
vanishes and the electric field assumes a Coulomb behavior with no trace of a
magnetic component. The connection to other monopole solutions, like Dirac`s,
t' Hooft`s or Poliakov`s types, are also discussed. Finally some speculative
remarks are presented in an attempt to explain such fields.Comment: 11 pages, 3 figures. In this version is update a permanent address of
the author L.P.G. De Assis and information on submission publication.
Submetted to International Journal of Theoretical Physic
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