25,258 research outputs found
Charging Interacting Rotating Black Holes in Heterotic String Theory
We present a formulation of the stationary bosonic string sector of the whole
toroidally compactified effective field theory of the heterotic string as a
double Ernst system which, in the framework of General Relativity describes, in
particular, a pair of interacting spinning black holes; however, in the
framework of low--energy string theory the double Ernst system can be
particularly interpreted as the rotating field configuration of two interacting
sources of black hole type coupled to dilaton and Kalb--Ramond fields. We
clarify the rotating character of the --component of the
antisymmetric tensor field of Kalb--Ramond and discuss on its possible torsion
nature. We also recall the fact that the double Ernst system possesses a
discrete symmetry which is used to relate physically different string vacua.
Therefore we apply the normalized Harrison transformation (a charging symmetry
which acts on the target space of the low--energy heterotic string theory
preserving the asymptotics of the transformed fields and endowing them with
multiple electromagnetic charges) on a generic solution of the double Ernst
system and compute the generated field configurations for the 4D effective
field theory of the heterotic string. This transformation generates the
vector field content of the whole low--energy heterotic string
spectrum and gives rise to a pair of interacting rotating black holes endowed
with dilaton, Kalb--Ramond and multiple electromagnetic fields where the charge
vectors are orthogonal to each other.Comment: 15 pages in latex, revised versio
Asymmetries in t tbar production: LHC versus Tevatron
The measurement of a charge asymmetry in t tbar production at LHC constitutes
more than an independent confirmation of the forward-backward asymmetry found
at Tevatron. Indeed, both measurements together can be used to identify the
source of the asymmetry. This is demonstrated for the case of new Z', W' vector
bosons and colour-sextet and triplet scalars, exchanged in t, u channels
respectively, and a very heavy axigluon in the s channel.Comment: LaTeX 5 pages. Updated with discussion on implications of summer
results. Final version to appear in PR
Coaxial Atomic Force Microscope Tweezers
We demonstrate coaxial atomic force microscope (AFM) tweezers that can trap
and place small objects using dielectrophoresis (DEP). An attractive force is
generated at the tip of a coaxial AFM probe by applying a radio frequency
voltage between the center conductor and a grounded shield; the origin of the
force is found to be DEP by measuring the pull-off force vs. applied voltage.
We show that the coaxial AFM tweezers (CAT) can perform three dimensional
assembly by picking up a specified silica microsphere, imaging with the
microsphere at the end of the tip, and placing it at a target destination.Comment: 9 pages, 3 figures, in review at Applied Physics Letter
Strong flavour changing effective operator contributions to single top quark production
We study the effects of dimension six effective operators on the production
of single top quarks at the LHC. The operator set considered includes terms
with effective gluon interactions and four-fermion terms. Analytic expressions
for the several partonic cross sections of single top production will be
presented, as well as the results of their integration on the parton density
functions.Comment: 20 pages, 7 fig
Asymmetries in top quark pair production at hadron colliders
We review the asymmetries in top quark pair production at the Tevatron and
the LHC. We summarize the experimental measurements and the interpretations of
a possible excess in terms of new physics. We also review other top quark
properties-emphasizing effects related to the asymmetries-as well as
other collider signals.Comment: RevTeX 40 pages. Final version to be published in Reviews of Modern
Physics, with several addition
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