87,650 research outputs found
Ultra-violet Finiteness in Noncommutative Supersymmetric Theories
We consider the ultra-violet divergence structure of general noncommutative
supersymmetric gauge theories, and seek theories which are all-orders
finite.Comment: 11 pages, Tex, one figure. Uses harvmac (big) and eps
Fayet-Iliopoulos D-terms and anomaly mediated supersymmetry breaking
We show that in a minimal extension of the MSSM by means of an extra U(1)
gauge group, the negative mass-squared problem characteristic of the Anomaly
Mediated Supersymmetry Breaking scenario is naturally solved by means of
Fayet-Iliopoulos D-terms. We derive a set of sum rules for the sparticle masses
which are consequences of the resulting framework.Comment: 11 pages, including 1 figure. Plain TeX. Uses Harvmac and epsf. Final
version to appear in Phys. Lett. B; some minor improvement
SRF cavity geometry optimization for the ILC with minimized surface e.m. fields and superior bandwidth
The main linacs of the ILC consist of nine-cell cavities based on the TESLA
design. In order to facilitate reaching higher gradients we have re-designed
the cavity shape. This leads to a reduction, comparable to several current
designs, in both the ratio of the surface electric field to the accelerating
field (Es/Ea) and the magnetic field to the accelerating field (Bs/Ea). The
bandwidth of the accelerating mode is also optimized. This new shape, which we
refer to as the New Low Surface Field (NLSF) design, bears comparison with the
Ichiro, Re-entrant and LSF designs.Comment: Presented at the 23rd Particle Accelerator Conference (PAC09)
Vancouver, Canad
The Exact Tachyon Beta-Function for the Wess-Zumino-Witten Model
We derive an exact expression for the tachyon -function for the
Wess-Zumino-Witten model. We check our result up to three loops by calculating
the three-loop tachyon -function for a general non-linear -model
with torsion, and then specialising to the case of the WZW model.Comment: 13pp, uses harvmac (with figures appended as a a standard PostScript
file), LTH 31
Quasi-infra-red fixed points and renormalisation group invariant trajectories for non-holomorphic soft supersymmetry breaking
In the MSSM the quasi-infra-red fixed point for the top-quark Yukawa coupling
gives rise to specific predictions for the soft-breaking parameters. We discuss
the extent to which these predictions are modified by the introduction of
additional ``non-holomorphic'' soft-breaking terms. We also show that in a
specific class of theories there exists an RG-invariant trajectory for the
``non-holomorphic'' terms, which can be understood using a holomorphic spurion
term.Comment: 24 pages, TeX, two figures. Uses Harvmac (big) and epsf. Minor errors
corrected, and the RG trajectory explained in terms of a holomorphic spurion
ter
The Gaugino \beta-Function
We present an elegant exact formula for the gaugino -function in a
softly-broken supersymmetric gauge theory, of the form , where is the gauge function and is
a simple differential operator acting on the gauge coupling and the Yukawa
coupling.Comment: 11 pages, tex, no figures. Uses harvmac. Minor error in derivation of
Eq. (14) correcte
Third Harmonic Cavity Modal Analysis
Third harmonic cavities have been designed and fabricated by FNAL to be used
at the FLASH/XFEL facility at DESY to minimise the energy spread along the
bunches. Modes in these cavities are analysed and the sensitivity to frequency
errors are assessed. A circuit model is employed to model the monopole bands.
The monopole circuit model is enhanced to include successive cell coupling, in
addition to the usual nearest neighbour coupling. A mode matching code is used
to facilitate rapid simulations, incorporating fabrication errors. Curves
surfaces are approximated by a series of abrupt transitions and the validity of
this approach is examinedComment: Proceedings of 14th International Conference on RF Superconductivity
(SRF 2009), 2009, Berlin, German
The effect of timing noise on targeted and narrow-band coherent searches for continuous gravitational waves from pulsars
Most searches for continuous gravitational-waves from pulsars use Taylor
expansions in the phase to model the spin-down of neutron stars. Studies of
pulsars demonstrate that their electromagnetic (EM) emissions suffer from
\emph{timing noise}, small deviations in the phase from Taylor expansion
models. How the mechanism producing EM emission is related to any continuous
gravitational-wave (CW) emission is unknown; if they either interact or are
locked in phase then the CW will also experience timing noise. Any disparity
between the signal and the search template used in matched filtering methods
will result in a loss of signal-to-noise ratio (SNR), referred to as
`mismatch'. In this work we assume the CW suffers a similar level of timing
noise to its EM counterpart. We inject and recover fake CW signals, which
include timing noise generated from observational data on the Crab pulsar.
Measuring the mismatch over durations of order months, the effect is
for the most part found to be small. This suggests recent so-called
`narrow-band' searches which placed upper limits on the signals from the Crab
and Vela pulsars will not be significantly affected. At a fixed observation
time, we find the mismatch depends upon the observation epoch. Considering the
averaged mismatch as a function of observation time, we find that it increases
as a power law with time, and so may become relevant in long baseline searches.Comment: 9 pages, 5 figure
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