13,895 research outputs found
Quantum Information Paradox: Real or Fictitious?
One of the outstanding puzzles of theoretical physics is whether quantum
information indeed gets lost in the case of Black Hole (BH) evaporation or
accretion. Let us recall that Quantum Mechanics (QM) demands an upper limit on
the acceleration of a test particle. On the other hand, it is pointed out here
that, if a Schwarzschild BH would exist, the acceleration of the test particle
would blow up at the event horizon in violation of QM. Thus the concept of an
exact BH is in contradiction of QM and quantum gravity (QG). It is also
reminded that the mass of a BH actually appears as an INTEGRATION CONSTANT of
Einstein equations. And it has been shown that the value of this integration
constant is actually zero. Thus even classically, there cannot be finite mass
BHs though zero mass BH is allowed. It has been further shown that during
continued gravitational collapse, radiation emanating from the contracting
object gets trapped within it by the runaway gravitational field. As a
consequence, the contracting body attains a quasi-static state where outward
trapped radiation pressure gets balanced by inward gravitational pull and the
ideal classical BH state is never formed in a finite proper time. In other
words, continued gravitational collapse results in an "Eternally Collapsing
Object" which is a ball of hot plasma and which is asymptotically approaching
the true BH state with M=0 after radiating away its entire mass energy. And if
we include QM, this contraction must halt at a radius suggested by highest QM
acceleration. In any case no EH is ever formed and in reality, there is no
quantum information paradox.Comment: 8 pages in Pramana Style, 6 in Revtex styl
On arbitrary-level IIR and FIR filters
A recently published method for designing IIR (infinite-impulse-response) digital filters with multilevel magnitude responses is reinterpreted from a different viewpoint. On the basis of this interpretation, techniques for extending these results to the case of finite-impulse-response (FIR) filters are developed. An advantage of the authors' method is that, when the arbitrary-level filter is implemented, its power-complementary filter, which may be required in specific applications, is obtained simultaneously. Also, by means of a tuning factor (a parameter of the scaling matrix), it is possible to generate a whole family of arbitrary-level filters
Evolution of Multipolar Magnetic Fields in Isolated Neutron Stars and its effect on Pulsar Radio Emission
The evolution of the multipolar structure of the magnetic field of isolated
neutron stars is studied assuming the currents to be confined to the crust.
Lower orders () of multipole are seen to evolve in a manner similar to
the dipole suggesting little or no evolution of the expected pulse shape. We
also study the multifrequency polarization position angle traverse of PSR
B0329+54 and find a significant frequency dependence above 2.7 GHz. We
interpret this as an evidence of strong multipolar magnetic field present in
the radio emission region.Comment: 2 pages, 2 figures, uses newpasp.sty, to appear in ASP Conf. Series,
IAU Coll. 177 on Pulsar Astronomy-2000 and Beyond, ed. M. Kramer, N. Wex, R.
Wielebinsk
Meanings in motion and faces: Developmental associations between the processing of intention from geometrical animations and gaze detection accuracy
Aspects of face processing, on the one hand, and theory of mind (ToM) tasks, on the other hand, show specific impairment in autism. We aimed to discover whether a correlation between tasks tapping these abilities was evident in typically developing children at two developmental stages. One hundred fifty-four normal children (6-8 years and 16-18 years) and 13 high-IQ autistic children (11-17 years) were tested on a range of face-processing and IQ tasks, and a ToM test based oil the attribution of intentional movement to abstract shapes in a cartoon. By midchildhood, the ability accurately and spontaneously to infer the locus of attention of a face with direct or averted gaze was specifically associated with the ability to describe geometrical animations using mental state terms. Other face-processing and animation descriptions failed to show the association. Autistic adolescents were impaired at both gaze processing and ToM descriptions. using these tests. Mentalizing and gaze perception accuracy are associated in typically developing children and adolescents. The findings are congruent with the possibility that common neural Circuitry underlies, at least in part, processing implicated in these tasks. They are also congruent with the possibility that autism may lie at one end of a developmental continuum with respect to these skills, and to the factor(s) underpinning them
Pulsar Radio Emission Altitude from Curvature Radiation
We assume that the relativistic sources moving along the dipolar magnetic
field lines emit curvature radiation. The beamed emission occurs in the
direction of tangents to the field lines, and to receive it, the sight line
must align with the tangent within the beaming angle 1/gamma, where gamma is
the particle Lorentz factor. By solving the viewing geometry in an inclined and
rotating dipole magnetic field, we show that, at any given pulse phase,
observer tends to receive radiation only from the specific heights allowed by
the geometry. We find outer conal components are emitted at higher altitudes
compared to inner components including the core. At any pulse phase, low
frequency emission comes from higher altitudes than high frequency emission. We
have modeled the emission heights of pulse components of PSR B0329+54, and
estimated field line curvature radii and particle Lorentz factors in the
emission regions.Comment: 14 pages, 3 figures. Accepted for Astrophysical Journal, 200
Cosmological Symmetry Breaking, Pseudo-scale invariance, Dark Energy and the Standard Model
The energy density of the universe today may be dominated by the vacuum
energy of a slowly rolling scalar field. Making a quantum expansion around such
a time dependent solution is found to break fundamental symmetries of quantum
field theory. We call this mechanism cosmological symmetry breaking and argue
that it is different from the standard phenomenon of spontaneous symmetry
breaking. We illustrate this with a toy scalar field theory, whose action
displays a U(1) symmetry. We identify a symmetry, called pseudo-scale
invariance, which sets the cosmological constant exactly equal to zero, both in
classical and quantum theory. This symmetry is also broken cosmologically and
leads to a nonzero vacuum or dark energy. The slow roll condition along with
the observed value of dark energy leads to a value of the background scalar
field of the order of Planck mass. We also consider a U(1) gauge symmetry
model. Cosmological symmetry breaking, in this case, leads to a non zero mass
for the vector field. We also show that a cosmologically broken pseudo-scale
invariance can generate a wide range of masses.Comment: 18 pages, no figure
3D-4D Interlinkage Of qqq Wave Functions Under 3D Support For Pairwise Bethe-Salpeter Kernels
Using the method of Green's functions within a Bethe-Salpeter framework
characterized by a pairwise qq interaction with a Lorentz-covariant 3D support
to its kernel, the 4D BS wave function for a system of 3 identical relativistic
spinless quarks is reconstructed from the corresponding 3D form which satisfies
a fully connected 3D BSE. This result is a 3-body generalization of a similar
2-body result found earlier under identical conditions of a 3D support to the
corresponding qq-bar BS kernel under Covariant Instaneity (CIA for short). (The
generalization from spinless to fermion quarks is straightforward).
To set the CIA with 3D BS kernel support ansatz in the context of
contemporary approaches to the qqq baryon problem, a model scalar 4D qqq BSE
with pairwise contact interactions to simulate the NJL-Faddeev equations is
worked out fully, and a comparison of both vertex functions shows that the CIA
vertex reduces exactly to the NJL form in the limit of zero spatial range. This
consistency check on the CIA vertex function is part of a fuller accounting for
its mathematical structure whose physical motivation is traceable to the role
of `spectroscopy' as an integral part of the dynamics.Comment: 20 pages, Latex, submitted via the account of K.-C. Yan
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