144,882 research outputs found
String Representation for the 't Hooft Loop Average in the Abelian Higgs Model
Making use of the duality transformation, we derive in the Londons' limit of
the Abelian Higgs Model string representation for the 't Hooft loop average
defined on the string world-sheet, which yields the values of two coefficient
functions parametrizing the bilocal correlator of the dual field strength
tensors. The asymptotic behaviours of these functions agree with the ones
obtained within the Method of Vacuum Correlators in QCD in the lowest order of
perturbation theory. We demonstrate that the bilocal approximation to the
Method of Vacuum Correlators is an exact result in the Londons' limit, i.e. all
the higher cumulants in this limit vanish. We also show that at large
distances, apart from the integration over metrics, the obtained string
effective theory (which in this case reduces to the nonlinear massive axionic
sigma model) coincides with the low-energy limit of the dual version of 4D
compact QED, the so-called Universal Confining String Theory. We derive string
tension of the Nambu-Goto term and the coupling constant of the rigidity term
for the obtained string effective theory and demonstrate that the latter one is
always negative, which means the stability of strings, while the positiveness
of the former is confirmed by the present lattice data. These data enable us to
find the Higgs boson charge and the vacuum expectation value of the Higgs
field, which model QCD best of all. We also study dynamics of the weight factor
of the obtained string representation for the 't Hooft average in the loop
space. In conclusion, we obtain string representation for the partition
function of the correlators of an arbitrary number of Higgs currents, by virtue
of which we rederive the structure of the bilocal correlator of the dual field
strength tensors, which yields the surface term in the string effective action.Comment: 11 pages, LaTeX, no figures, references are adde
Observation potential for \chi_b at the Tevatron and LHC
We confirm the results of previous works that the internal motion of quarks
inside charmonium mesons increases the cross section of the process J/\psi\eta_c\chi_{b0,2}\to2J/\psi$ can be used to detect these scalar mesons at Tevatron
and LHC colliders.Comment: 13 pages, 5 figures, error in fig.3 correcte
Current responses and voltage fluctuations in Josephson-junction systems
We consider arrays of Josephson junctions as well as single junctions in both
the classical and quantum-mechanical regimes, and examine the generalized
(frequency-dependent) resistance, which describes the dynamic responses of such
Josephson-junction systems to external currents. It is shown that the
generalized resistance and the power spectrum of voltage fluctuations are
related via the fluctuation-dissipation theorem. Implications of the obtained
relations are also discussed in various experimental situations.Comment: 4 pages, To appear in Europhys. Let
Fluorine in a Carbon-Enhanced Metal-Poor Star
The fluorine abundance of the Carbon-Enhanced Metal-Poor (CEMP) star HE
1305+0132 has been derived by analysis of the molecular HF (1-0) R9 line at
2.3357 microns in a high-resolution (R = 50,000) spectrum obtained with the
Phoenix spectrometer and Gemini-South telescope. Our abundance analysis makes
use of a CNO-enhanced ATLAS12 model atmosphere characterized by a metallicity
and CNO enhancements determined utilizing medium-resolution (R = 3,000) optical
and near-IR spectra. The effective iron abundance is found to be [Fe/H] = -2.5,
making HE 1305+0132 the most Fe-deficient star, by more than an order of
magnitude, for which the abundance of fluorine has been measured. Using
spectral synthesis, we derive a super-solar fluorine abundance of A(19F) = 4.96
+/- 0.21, corresponding to a relative abundance of [F/Fe] = 2.90. A single line
of the Phillips C_2 system is identified in our Phoenix spectrum, and along
with multiple lines of the first-overtone vibration-rotation CO (3-1) band
head, C and O abundances of A(12C) = 8.57 +/- 0.11 and A(16O) = 7.04 +/- 0.14
are derived. We consider the striking fluorine overabundance in the framework
of the nucleosynthetic processes thought to be responsible for the
C-enhancement of CEMP stars and conclude that the atmosphere of HE 1305+0132
was polluted via mass transfer by a primary companion during its asymptotic
giant branch phase. This is the first study of fluorine in a CEMP star, and it
demonstrates that this rare nuclide can be a key diagnostic of nucleosynthetic
processes in the early Galaxy.Comment: 13 pages, 3 figures; Accepted for publication in ApJ Letter
A low-noise ferrite magnetic shield
Ferrite materials provide magnetic shielding performance similar to commonly
used high permeability metals but have lower intrinsic magnetic noise generated
by thermal Johnson currents due to their high electrical resistivity.
Measurements inside a ferrite shield with a spin-exchange relaxation-free
atomic magnetometer reveal a noise level of 0.75 fT Hz^(-1/2), 25 times lower
than what would be expected in a comparable mu-metal shield. The authors
identify a 1/f component of the magnetic noise due to magnetization
fluctuations and derive general relationships for the Johnson current noise and
magnetization noise in cylindrical ferromagnetic shields in terms of their
conductivity and complex magnetic permeability.Comment: 4 pages, 3 figures. Published in Appl. Phys. Lett.; replacement
reflects published wor
Light Gravitinos at Colliders and Implications for Cosmology
Light gravitinos, with mass in the eV to MeV range, are well-motivated in
particle physics, but their status as dark-matter candidates is muddled by
early-Universe uncertainties. We investigate how upcoming data from colliders
may clarify this picture. Light gravitinos are produced primarily in the decays
of the next-to-lightest supersymmetric particle, resulting in spectacular
signals, including di-photons, delayed and non-pointing photons, kinked charged
tracks, and heavy metastable charged particles. We find that the Tevatron with
20/fb and the 7 TeV LHC with 1/fb may both see evidence for hundreds of
light-gravitino events. Remarkably, this collider data is also well suited to
distinguish between currently viable light-gravitino scenarios, with striking
implications for structure formation, inflation, and other early-Universe
cosmology.Comment: 12 pages, 6 figures. To be submitted to Phys. Rev. D
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