771 research outputs found
ADM approach to 2+1 dimensional gravity coupled to particles
We develop the canonical ADM approach to 2+1 dimensional gravity in presence
of point particles. The instantaneous York gauge can be applied for open
universes or universes with the topology of the sphere. The sequence of
canonical ADM equations is solved in terms of the conformal factor. A simple
derivation is given for the solution of the two body problem. A geometrical
characterization is given for the apparent singularities occurring in the
N-body problem and it is shown how the Garnier hamiltonian system arises in the
ADM treatment by considering the time development of the conformal factor at
the locations where the extrinsic curvature tensor vanishes.Comment: 34 pages, LaTe
Effective Values of Komar Conserved Quantities and Their Applications
We calculate the effective Komar angular momentum for the Kerr-Newman (KN)
black hole. This result is valid at any radial distance on and outside the
black hole event horizon. The effcetive values of mass and angular momentum are
then used to derive an identity () which relates the Komar
conserved charge () corresponding to the null Killing vector
() with the thermodynamic quantities of this black hole. As an
application of this identity the generalised Smarr formula for this black hole
is derived. This establishes the fact that the above identity is a local form
of the inherently non-local generalised Smarr formula.Comment: v3, minor modifications over v2; LaTex, 9 pages, no figures, to
appear in Int. Jour. Theo. Phy
Mild place illusion: a virtual reality factor to spark creativity in writing
Developments in Virtual Reality (VR) technology have modified
the creative potential of each individual. We introduce a new con cept, called "mild place illusion", as a new paradigm for designing
VR-based user interfaces targeted at stimulating creativity. We
show that for creative tasks - such as creative writing, new product
ideation, and brainstorming - a "just-enough" amount of place illu sion leads to a greater self-perception of creativity, as opposed to a
"full-level" place illusion. This is a somewhat unexpected result
since one would suppose, a priori, to have the full-level place illu sion as the optimal setup for stimulating creativity. We considered
that the methodology in this work was fairly complex, but our re sults show â through a data triangulation approach â that we were
able to identify more consistent and personal creative experiences.
Therefore, the main contribution of this paper is a new paradigm
for designing VR user interfaces targeted at stimulating creativity
by showing that a âone-illusion interspaceâ leads to a greater self perception of creativity.info:eu-repo/semantics/publishedVersio
Spherically symmetric vacuum solutions of modified gravity theory in higher dimensions
In this paper we investigate spherically symmetric vacuum solutions of
gravity in a higher dimensional spacetime. With this objective we construct a
system of non-linear differential equations, whose solutions depend on the
explicit form assumed for the function . We explicit
show that for specific classes of this function exact solutions from the field
equations are obtained; also we find approximated results for the metric tensor
for more general cases admitting close to the unity.Comment: 14 pages, no figure. New version accepted for publication in EPJ
Orbital dependent nucleonic pairing in the lightest known isotopes of tin
By studying the 109Xe-->105Te-->101Sn superallowed alpha-decay chain, we
observe low-lying states in 101Sn, the one-neutron system outside doubly magic
100Sn. We find that the spins of the ground state (J = 7=2) and first excited
state (J = 5=2) in 101Sn are reversed with respect to the traditional level
ordering postulated for 103Sn and the heavier tin isotopes. Through simple
arguments and state-of-the-art shell model calculations we explain this
unexpected switch in terms of a transition from the single-particle regime to
the collective mode in which orbital-dependent pairing correlations, dominate.Comment: 5 pages 3 figure
Gravitational collapse in asymptotically Anti-de Sitter/de Sitter backgrounds
We study here the gravitational collapse of a matter cloud with a
non-vanishing tangential pressure in the presence of a non-zero cosmological
term. Conditions for bounce and singularity formation are derived for the
model. It is also shown that when the tangential pressures vanish, the bounce
and singularity conditions reduce to that of the dust case studied earlier. The
collapsing interior is matched with an exterior which is asymptotically de
Sitter or anti de Sitter, depending on the sign of cosmological constant. The
junction conditions for matching the cloud to exterior are specified. The
effect of the cosmological term on apparent horizons is studied in some detail,
and the nature of central singularity is analyzed. We also discuss here the
visibility of the singularity and implications for the cosmic censorship
conjecture.Comment: 11 pages, 1 figure, Revtex
Neutron star in presence of torsion-dilaton field
We develop the general theory of stars in Saa's model of gravity with
propagating torsion and study the basic stationary state of neutron star. Our
numerical results show that the torsion force decreases the role of the gravity
in the star configuration leading to significant changes in the neutron star
masses depending on the equation of state of star matter. The inconsistency of
the Saa's model with Roll-Krotkov-Dicke and Braginsky-Panov experiments is
discussed.Comment: 29 pages, latex, 24 figures, final version. Added: 1)comments on
different possible mass definitions; 2)new sections: a)the inconsistency of
the Saa's model with Roll-Krotkov-Dicke and Braginsky-Panov experiments;
b)stability analysis via catastrophe theory; 3)new figers added and some
figures replaced. 4)new reference
On the K^+D Interaction at Low Energies
The Kd reactions are considered in the impulse approximation with NN
final-state interactions (NN FSI) taken into account. The realistic parameters
for the KN phase shifts are used. The "quasi-elastic" energy region, in which
the elementary KN interaction is predominantly elastic, is considered. The
theoretical predictions are compared with the data on the K^+d->K^+pn,
K^+d->K^0pp, K^+d->K^+d and K^+d total cross sections. The NN FSI effect in the
reaction K^+d->K^+pn has been found to be large. The predictions for the Kd
cross sections are also given for slow kaons, produced from phi(1020) decays,
as the functions of the isoscalar KN scattering length a_0. These predictions
can be used to extract the value of a_0 from the data.Comment: 22 pages, 5 figure
On the Delta-Nucleon and Rho - Pi Splittings: A QCD-inspired Look in Free Hadrons versus Nuclei
Relationships between mass intervals for free hadrons and in nuclei are
studied in two theoretical approaches inspired by QCD: naive quark model and
skyrmion model, taking one example each from mesons and baryons, that of pi-rho
splitting in mesons, and nucleon-Delta splitting in baryons. Possible
deconfinement effects in nuclei are examined.Comment: 16 pages, LaTe
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