1,124 research outputs found
Veneziano Amplitude for Winding Strings
String configurations with nonzero winding number describe soliton string
states. We compute the Veneziano amplitude for the scattering of arbitrary
winding states and show that in the large radius limit the strings always
scatter trivially and with no change in the individual winding numbers of the
strings. In this limit, then, these states scatter as true solitons.Comment: 7 page
A Comment on String Solitons
We derive an exact string-like soliton solution of D=10 heterotic string
theory. The solution possesses instanton structure in the
eight-dimensional space transverse to the worldsheet of the soliton.Comment: 4 page
Nonexistence of Generalized Apparent Horizons in Minkowski Space
We establish a Positive Mass Theorem for initial data sets of the Einstein
equations having generalized trapped surface boundary. In particular we answer
a question posed by R. Wald concerning the existence of generalized apparent
horizons in Minkowski space
Dynamics of Extreme Black Holes and Massive String States
In a recent paper, Duff and Rahmfeld argued that certain massive
states of the four-dimensional heterotic string correspond to extreme black
hole solutions. We provide further, dynamical, evidence for this identification
by comparing the scattering of these elementary string states with that of the
corresponding extreme black holes, in the limit of low velocities.Comment: 18 pages, harvma
A Bakry-\'Emery Almost Splitting Result With Applications to the Topology of Black Holes
The almost splitting theorem of Cheeger-Colding is established in the setting
of almost nonnegative generalized -Bakry-\'{E}mery Ricci curvature, in which
is positive and the associated vector field is not necessarily required to
be the gradient of a function. In this context it is shown that with a diameter
upper bound and volume lower bound the fundamental group of such manifolds is
almost abelian. Furthermore, extensions of well-known results concerning Ricci
curvature lower bounds are given for generalized -Bakry-\'{E}mery Ricci
curvature. These include: the first Betti number bound of Gromov and Gallot,
Anderson's finiteness of fundamental group isomorphism types, volume
comparison, the Abresch-Gromoll inequality, and a Cheng-Yau gradient estimate.
Finally, this analysis is applied to stationary vacuum black holes in higher
dimensions to find that low temperature horizons must have limited topology,
similar to the restrictions exhibited by (extreme) horizons of zero
temperature.Comment: Comm. Math. Phys., to appea
Kaluza-Klein and H-Dyons in String Theory
Kaluza-Klein monopole and H-monopole solutions, which are T-dual to each
other, are the well-known solutions of string theory compactified on .
Since string theory in this case has an S-duality symmetry, we explicitly
construct the corresponding dyonic solutions by expressing the string
effective action in a manifestly invariant form with an
invariant constraint. The Schwarz-Sen charge spectrum, the BPS saturated mass
formula as well as the stability of these states are discussed briefly.Comment: 15 pages, LaTeX, No figures, improved version to appear in Phys. Rev.
WHY THE REAL PART OF THE PROTON-PROTON FORWARD SCATTERING AMPLITUDE SHOULD BE MEASURED AT THE LHC
4p, 2figs, Contribution to EDS2005, Blois May 2005For the energy of 14 TeV, to be reached at the Large Hadron Collider (LHC), we have had for some time accurate predictions for both the real and imaginary parts of the forward proton-proton elastic scattering amplitude. LHC is now scheduled to start operating in two years, and it is timely to discuss some of the important consequences of the measurements of both the total cross-section and the ratio of the real to the imaginary part. We stress the importance of measuring the real part of the proton-proton forward scattering amplitude at LHC, because a deviation from existing theoretical predictions could be a strong sign for new physics
Brane Effects on Extra Dimensional Scenarios: A Tale of Two Gravitons
We analyze the propagation of a scalar field in multidimensional theories
which include kinetic corrections in the brane, as a prototype for
gravitational interactions in a four dimensional brane located in a (nearly)
flat extra dimensional bulk. We regularize the theory by introducing an
infrared cutoff given by the size of the extra dimensions and a physical
ultraviolet cutoff of the order of the fundamental Planck scale in the higher
dimensional theory. We show that, contrary to recent suggestions, the radius of
the extra dimensions cannot be arbitrarily large. Moreover, for finite radii,
the gravitational effects localized on the brane can substantially alter the
phenomenology of collider and/or table-top gravitational experiments. This
phenomenology is dictated by the presence of a massless graviton, with standard
couplings to the matter fields, and a massive graviton which couples to matter
in a much stronger way. While graviton KK modes lighter than the massive
graviton couple to matter in a standard way, the couplings to matter of the
heavier KK modes are strongly suppressed.Comment: 21 pages, latex2e, axodraw.sty, 2 figure
More on Four-Dimensional Extremal Black Holes
We consider an embedding of the extremal four-dimensional
Reissner-Nordstr\"om black hole into type string theory. The equivalent
type configuration, in the D-brane weak-coupling picture, is a bound
state of D1- and D5-branes threaded by fundamental type strings. The
bound state involves also a NSNS solitonic 5-brane, mimicking the role of the
Kaluza-Klein magnetic monopole. The statistical entropy derived by counting the
degeneracy of the BPS-saturated excitations of this bound state agrees
perfectly with the (semiclassical) Bekenstein-Hawking formula.Comment: 19 pages, using Latex, no figure
Monopoles and Instantons in String Theory
In recent work, several classes of solitonic solutions of string theory with
higher-membrane structure have been obtained. These solutions can be classified
according to the symmetry possessed by the solitons in the subspace of the
spacetime transverse to the membrane. Solitons with four-dimensional spherical
symmetry represent instanton solutions in string theory, while those with
three-dimensional spherical symmetry represent magnetic monopole-type
solutions. For both of these classes, we discuss bosonic as well as heterotic
solutions.Comment: 16 page
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