1,660 research outputs found
Extremal Isolated Horizons: A Local Uniqueness Theorem
We derive all the axi-symmetric, vacuum and electrovac extremal isolated
horizons. It turns out that for every horizon in this class, the induced metric
tensor, the rotation 1-form potential and the pullback of the electromagnetic
field necessarily coincide with those induced by the monopolar, extremal
Kerr-Newman solution on the event horizon. We also discuss the general case of
a symmetric, extremal isolated horizon. In particular, we analyze the case of a
two-dimensional symmetry group generated by two null vector fields. Its
relevance to the classification of all the symmetric isolated horizons,
including the non-extremal once, is explained.Comment: 22 pages, page size changed, typos and equations (142), (143a)
corrected, PACS number adde
Lukewarm black holes in quadratic gravity
Perturbative solutions to the fourth-order gravity describing
spherically-symmetric, static and electrically charged black hole in an
asymptotically de Sitter universe is constructed and discussed. Special
emphasis is put on the lukewarm configurations, in which the temperature of the
event horizon equals the temperature of the cosmological horizon
Twistorial versus space--time formulations: unification of various string models
We introduce the D=4 twistorial tensionfull bosonic string by considering the
canonical twistorial 2--form in two--twistor space. We demonstrate its
equivalence to two bosonic string models: due to Siegel (with covariant
worldsheet vectorial string momenta ) and the one with
tensorial string momenta . We show how to obtain in
mixed space-time--twistor formulation the Soroka--Sorokin--Tkach--Volkov (SSTV)
string model and subsequently by harmonic gauge fixing the Bandos--Zheltukhin
(BZ) model, with constrained spinorial coordinates.Comment: RevTex4,APS, 4 pages. The version which appears in Phys. Rev.
Topological quantum D-branes and wild embeddings from exotic smooth R^4
This is the next step of uncovering the relation between string theory and
exotic smooth R^4. Exotic smoothness of R^4 is correlated with D6 brane charges
in IIA string theory. We construct wild embeddings of spheres and relate them
to a class of topological quantum Dp-branes as well to KK theory. These branes
emerge when there are non-trivial NS-NS H-fluxes where the topological classes
are determined by wild embeddings S^2 -> S^3. Then wild embeddings of higher
dimensional -complexes into S^n correspond to Dp-branes. These wild
embeddings as constructed by using gropes are basic objects to understand
exotic smoothness as well Casson handles. Next we build C*-algebras
corresponding to the embeddings. Finally we consider topological quantum
D-branes as those which emerge from wild embeddings in question. We construct
an action for these quantum D-branes and show that the classical limit agrees
with the Born-Infeld action such that flat branes = usual embeddings.Comment: 18 pages, 1 figur
Extension of the Shirafuji model for Massive Particles with Spin
We extend the Shirafuji model for massless particles with primary spacetime
coordinates and composite four-momenta to a model for massive particles with
spin and electric charge. The primary variables in the model are the spacetime
four-vector, four scalars describing spin and charge degrees of freedom as well
as a pair of Weyl spinors. The geometric description proposed in this paper
provides an intermediate step between the free purely twistorial model in
two-twistor space in which both spacetime and four-momenta vectors are
composite, and the standard particle model, where both spacetime and
four-momenta vectors are elementary. We quantize the model and find explicitly
the first-quantized wavefunctions describing relativistic particles with mass,
spin and electric charge. The spacetime coordinates in the model are not
commutative; this leads to a wavefunction that depends only on one covariant
projection of the spacetime four-vector (covariantized time coordinate)
defining plane wave solutions.Comment: Latex, 27 pages, appendix.sty, newlfont.sty (attached
Electrons as quasi-bosons in magnetic white dwarfs
A white dwarf star achieves its equilibrium from the balancing of the
gravitational compression against the Fermi degeneracy pressure of the electron
gas. In field theory there are examples (e.g. the monopole-charge system) where
a strong magnetic field can transform a boson into a fermion or a fermion into
a boson. In some condensed matter systems (e.g. fractional quantum Hall
systems) a strong magnetic field can transform electrons into effective
fermions, or effective anyons. Based on these examples we investigate the
possibility that the strong magnetic fields of some white dwarfs may transform
some fraction of the electrons into effective bosons. This could have
consequences for the structure of highly magnetized white dwarfs. It would
alter the mass-radius relationship, and in certain instances one could envision
a scenario where a white dwarf below the Chandrasekhar limit could nevertheless
collapse into a neutron star due to a weakening of the electron degeneracy
pressure. In addition the transformation of electrons into effective bosons
could result in the electrons Bose condensing, which could speed up the cooling
rate of white dwarfs.Comment: 10 pages. To be published IJMP
The Free Particle in Deformed Special Relativity
The phase space of a classical particle in DSR contains de Sitter space as
the space of momenta. We start from the standard relativistic particle in five
dimensions with an extra constraint and reduce it to four dimensional DSR by
imposing appropriate gauge fixing. We analyze some physical properties of the
resulting theories like the equations of motion, the form of Lorentz
transformations and the issue of velocity. We also address the problem of the
origin and interpretation of different bases in DSR.Comment: 15 page
Distinguished Cp(X) spaces
We continue our initial study of Cp(X) spaces that are distinguished, equiv., are large subspaces
of RX , equiv., whose strong duals Lβ(X) carry the strongest locally convex topology.
Many are distinguished, many are not. All Lβ(X) spaces are, as are all metrizable Cp(X)
and Ck (X) spaces. To prove a space Cp(X) is not distinguished, we typically compare the
character of Lβ(X) with |X|. A certain covering for X we call a scant cover is used to find
distinguished Cp(X) spaces. Two of the main results are: (i) Cp(X) is distinguished if and
only if its bidual E coincides with RX , and (ii) for a Corson compact space X, the space
Cp(X) is distinguished if and only if X is scattered and Eberlein compact
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