1,587 research outputs found
Magnetic field generation in Higgs inflation model
We study the generation of magnetic field in Higgs-inflation models where the
Standard Model Higgs boson has a large coupling to the Ricci scalar. We couple
the Higgs field to the Electromagnetic fields via a non- renormalizable
dimension six operator suppressed by the Planck scale in the Jordan frame. We
show that during Higgs inflation magnetic fields with present value
Gauss and comoving coherence length of can be generated in the
Einstein frame. The problem of large back-reaction which is generic in the
usual inflation models of magneto-genesis is avoided as the back-reaction is
suppressed by the large Higgs-curvature coupling.Comment: 10 pages, RevTeX
Radionic Non-uniform Black Strings
Non-uniform black strings in the two-brane system are investigated using the
effective action approach. It is shown that the radion acts as a non-trivial
hair of the black strings. From the brane point of view, the black string
appears as the deformed dilatonic black hole which becomes dilatonic black hole
in the single brane limit and reduces to the Reissner-Nordstr\"om black hole in
the close limit of two-branes. The stability of solutions is demonstrated using
the catastrophe theory. From the bulk point of view, the black strings are
proved to be non-uniform. Nevertheless, the zeroth law of black hole
thermodynamics still holds.Comment: 9 pages, 6 figure
Characterization of charge collection in CdTe and CZT using the transient current technique
The charge collection properties in different particle sensor materials with
respect to the shape of the generated signals, the electric field within the
detector, the charge carrier mobility and the carrier lifetime are studied with
the transient current technique (TCT). Using the well-known properties of Si as
a reference, the focus is laid on Cadmium-Telluride (CdTe) and
Cadmium-Zinc-Telluride (CZT), which are currently considered as promising
candidates for the efficient detection of X-rays. All measurements are based on
a transient-current technique (TCT) setup, which allows the recording of
current pulses generated by an 241Am alpha-source. These signals will be
interpreted with respect to the build-up of space-charges inside the detector
material and the subsequent deformation of the electric field. Additionally the
influence of different electrode materials (i.e. ohmic or Schottky contacts) on
the current pulse shapes will be treated in the case of CdTe. Finally, the
effects of polarization, i.e. the time-dependent degradation of the detector
signals due to the accumulation of fixed charges within the sensor, are
presented.Comment: 20 pages, 17 figure
't Hooft Operators in Gauge Theory from Toda CFT
We construct loop operators in two dimensional Toda CFT and calculate with
them the exact expectation value of certain supersymmetric 't Hooft and dyonic
loop operators in four dimensional \Ncal=2 gauge theories with SU(N) gauge
group. Explicit formulae for 't Hooft and dyonic operators in \Ncal=2^* and
\Ncal=2 conformal SQCD with SU(N) gauge group are presented. We also briefly
speculate on the Toda CFT realization of arbitrary loop operators in these
gauge theories in terms of topological web operators in Toda CFT.Comment: 49 pages, LaTeX. Typos fixed, references adde
Geometry and cosmological perturbations in the bulk inflaton model
We consider a braneworld inflation model driven by the dynamics of a scalar
field living in the 5-dimensional bulk, the so-called ``bulk inflaton model'',
and investigate the geometry in the bulk and large scale cosmological
perturbations on the brane. The bulk gravitational effects on the brane are
described by a projection of the 5-dimensional Weyl tensor, which we denote by
. Focusing on a tachionic potential model, we take a perturbative
approach in the anti-de Sitter (AdS) background with a single de Sitter
brane. We first formulate the evolution equations for in the bulk.
Next, applying them to the case of a spatially homogeneous brane, we obtain two
different integral expressions for . One of them reduces to the
expression obtained previously when evaluated on the brane. The other is a new
expression that may be useful for analyzing the bulk geometry. Then we consider
superhorizon scale cosmological perturbations and evaluate the bulk effects
onto the brane. In the limit , where is the Hubble parameter
on the brane and is the bulk curvature radius, we find that the
effective theory on the brane is identical to the 4-dimensional Einstein-scalar
theory with a simple rescaling of the potential even under the presence of
inhomogeneities. % atleast on super-Hubble horizon scales. In particular, it is
found that the anticipated non-trivial bulk effect due to the spatially
anisotropic part of may appear only at %second order in the low
energy expansion, i.e., at .Comment: 21 pages including 6 pages for several appendixes, no figure
Radion and Holographic Brane Gravity
The low energy effective theory for the Randall-Sundrum two brane system is
investigated with an emphasis on the role of the non-linear radion in the brane
world. The equations of motion in the bulk is solved using a low energy
expansion method. This allows us, through the junction conditions, to deduce
the effective equations of motion for the gravity on the brane. It is shown
that the gravity on the brane world is described by a quasi-scalar-tensor
theory with a specific coupling function omega(Psi) = 3 Psi / 2(1-Psi) on the
positive tension brane and omega(Phi) = -3 Phi / 2(1+Phi) on the negative
tension brane, where Psi and Phi are non-linear realizations of the radion on
the positive and negative tension branes, respectively. In contrast to the
usual scalar-tensor gravity, the quasi-scalar-tensor gravity couples with two
kinds of matter, namely, the matters on both positive and negative tension
branes, with different effective gravitational coupling constants. In
particular, the radion disguised as the scalar fields Psi and Phi couples with
the sum of the traces of the energy momentum tensor on both branes. In the
course of the derivation, it has been revealed that the radion plays an
essential role to convert the non-local Einstein gravity with the generalized
dark radiation to the local quasi-scalar-tensor gravity. For completeness, we
also derive the effective action for our theory by substituting the bulk
solution into the original action. It is also shown that the
quasi-scalar-tensor gravity works as holograms at the low energy in the sense
that the bulk geometry can be reconstructed from the solution of the
quasi-scalar-tensor gravity.Comment: Revtex4, 18 pages, revised version, conclusions unchanged, references
adde
Gauge Theory Wilson Loops and Conformal Toda Field Theory
The partition function of a family of four dimensional N=2 gauge theories has
been recently related to correlation functions of two dimensional conformal
Toda field theories. For SU(2) gauge theories, the associated two dimensional
theory is A_1 conformal Toda field theory, i.e. Liouville theory. For this case
the relation has been extended showing that the expectation value of gauge
theory loop operators can be reproduced in Liouville theory inserting in the
correlators the monodromy of chiral degenerate fields. In this paper we study
Wilson loops in SU(N) gauge theories in the fundamental and anti-fundamental
representation of the gauge group and show that they are associated to
monodromies of a certain chiral degenerate operator of A_{N-1} Toda field
theory. The orientation of the curve along which the monodromy is evaluated
selects between fundamental and anti-fundamental representation. The analysis
is performed using properties of the monodromy group of the generalized
hypergeometric equation, the differential equation satisfied by a class of four
point functions relevant for our computation.Comment: 17 pages, 3 figures; references added
Probing polarization states of primordial gravitational waves with CMB anisotropies
We discuss the polarization signature of primordial gravitational waves
imprinted in cosmic microwave background (CMB) anisotropies. The high-energy
physics motivated by superstring theory or M-theory generically yield parity
violating terms, which may produce a circularly polarized gravitational wave
background (GWB) during inflation. In contrast to the standard prediction of
inflation with un-polarized GWB, circularly polarized GWB generates
non-vanishing TB and EB-mode power spectra of CMB anisotropies. We evaluate the
TB and EB-mode power spectra taking into account the secondary effects and
investigate the dependence of cosmological parameters. We then discuss current
constraints on the circularly polarized GWB from large angular scales (l < 16)
of the three year WMAP data. Prospects for future CMB experiments are also
investigated based on a Monte Carlo analysis of parameter estimation, showing
that the circular polarization degree, varepsilon, which is the asymmetry of
the tensor power spectra between right- and left-handed modes normalized by the
total amplitude, can be measured down to |varepsilon| 0.35(r/0.05)^{-0.6}.Comment: 28 pages, 9 figures, Accepted for publication in JCA
Controlling suction by vapour equilibrium technique at different temperatures, application to the determination of the water retention properties of MX80 clay
Problems related to unsaturated soils are frequently encountered in
geotechnical or environmental engineering works. In most cases, for the purpose
of simplicity, the problems are studied by considering the suction effects on
volume change or shear strength under isothermal conditions. Under isothermal
condition, very often, a temperature independent water retention curve is
considered in the analysis, which is obviously a simplification. When the
temperature changes are too significant to be neglected, it is necessary to
account for the thermal effects. In this paper, a method for controlling
suction using the vapour equilibrium technique at different temperatures is
presented. First, calibration of various saturated saline solutions was carried
out from temperature of 20 degrees C to 60 degrees C. A mirror psychrometer was
used for the measurement of relative humidity generated by saturated saline
solutions at different temperatures. The results obtained are in good agreement
with the data from the literature. This information was then used to determine
the water retention properties of MX80 clay, which showed that the retention
curve is shifting down with increasing of temperature
N=2 Supersymmetric Model with Dirac-Kahler Fermions from Generalized Gauge Theory in Two Dimensions
We investigate the generalized gauge theory which has been proposed
previously and show that in two dimensions the instanton gauge fixing of the
generalized topological Yang-Mills action leads to a twisted N=2 supersymmetric
action. We have found that the R-symmetry of N=2 supersymmetry can be
identified with the flavour symmetry of Dirac-Kahler fermion formulation. Thus
the procedure of twist allows topological ghost fields to be interpreted as the
Dirac-Kahler matter fermions.Comment: 22 pages, LaTe
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