1,378 research outputs found
Simultaneous ground-based and satellite observations of natural VLF waves in Antarctica: A case study of downward ionospheric penetration of whistler-mode waves
AbstractTo investigate downward ionospheric-penetration characteristics of VLF (several hundred Hz to 17.8 kHz) whistler-mode waves, we conducted simultaneous observations (in 2006) of natural VLF waves using both ground stations in Antarctica and the Japanese Akebono satellite. The ground-based and satellite observations included an interesting event for which both observed similar VLF waves. In this study, we theoretically calculate down-going whistler-mode wave propagation based on ground-satellite observations using the full-wave analysis. In a case study, the observed wave-normal angles were approximately 140–160 degrees for a dayside chorus event on 15 March 2006. The theoretical calculation showed that the wave-normal angles for ionospheric penetration should be around 155.6 degrees, with its angular width of approximately 2 degrees. Moreover, the wave-energy loss due to ionospheric penetration is estimated at 20.4 dB based on our theoretical calculation, in accordance with the observed 17–19 dB
Induced Gravity as a WZNW Model
We derive the explicit form of the Wess-Zumino quantum effective action of
chiral \Winf-symmetric system of matter fields coupled to a general chiral
\Winf-gravity background. It is expressed as a geometric action on a
coadjoint orbit of the deformed group of area-preserving diffeomorphisms on
cylinder whose underlying Lie algebra is the centrally-extended algebra of
symbols of differential operators on the circle. Also, we present a systematic
derivation, in terms of symbols, of the "hidden" SL(\infty;\IR) Kac-Moody
currents and the associated SL(\infty;\IR) Sugawara form of energy-momentum
tensor component as a consequence of the SL(\infty;\IR) stationary
subgroup of the relevant \Winf coadjoint orbit
Quantum Electrodynamics at Extremely Small Distances
The asymptotics of the Gell-Mann - Low function in QED can be determined
exactly, \beta(g)= g at g\to\infty, where g=e^2 is the running fine structure
constant. It solves the problem of pure QED at small distances L and gives the
behavior g\sim L^{-2}.Comment: Latex, 6 pages, 1 figure include
Iterative algorithms for total variation-like reconstructions in seismic tomography
A qualitative comparison of total variation like penalties (total variation,
Huber variant of total variation, total generalized variation, ...) is made in
the context of global seismic tomography. Both penalized and constrained
formulations of seismic recovery problems are treated. A number of simple
iterative recovery algorithms applicable to these problems are described. The
convergence speed of these algorithms is compared numerically in this setting.
For the constrained formulation a new algorithm is proposed and its convergence
is proven.Comment: 28 pages, 8 figures. Corrected sign errors in formula (25
The renormalization group and spontaneous compactification of a higher-dimensional scalar field theory in curved spacetime
The renormalization group (RG) is used to study the asymptotically free
-theory in curved spacetime. Several forms of the RG equations for
the effective potential are formulated. By solving these equations we obtain
the one-loop effective potential as well as its explicit forms in the case of
strong gravitational fields and strong scalar fields. Using zeta function
techniques, the one-loop and corresponding RG improved vacuum energies are
found for the Kaluza-Klein backgrounds and . They are given in terms of exponentially convergent series, appropriate
for numerical calculations. A study of these vacuum energies as a function of
compactification lengths and other couplings shows that spontaneous
compactification can be qualitatively different when the RG improved energy is
used.Comment: LaTeX, 15 pages, 4 figure
Is aromatase necessary for ovarian differentiation in tambaqui (Colossoma macropomum)?
Here we report for the first time the identification, characterization and expression of Cyp19a and Cyp19b in tambaqui (Colossoma macropomum) during sex differentiation
Dynamics of Monopoles and Flux Tubes in Two-Flavor Dynamical QCD
We investigate the confining properties of the QCD vacuum with
flavors of dynamical quarks, and compare the results with the properties of the
quenched theory. We use non-perturbatively improved Wilson
fermions to keep cut-off effects small. We focus on color magnetic monopoles.
Among the quantities we study are the monopole density and the monopole
screening length, the static potential and the profile of the color electric
flux tube. We furthermore derive the low-energy effective monopole action.
Marked differences between the quenched and dynamical vacuum are found.Comment: 34 pages, 28 figures, Late
Two-loop effective potential for a general renormalizable theory and softly broken supersymmetry
I compute the two-loop effective potential in the Landau gauge for a general
renormalizable field theory in four dimensions. Results are presented for the
\bar{MS} renormalization scheme based on dimensional regularization, and for
the \bar{DR} and \bar{DR}' schemes based on regularization by dimensional
reduction. The last of these is appropriate for models with softly broken
supersymmetry, such as the Minimal Supersymmetric Standard Model. I find the
parameter redefinition which relates the \bar{DR} and \bar{DR}' schemes at
two-loop order. I also discuss the renormalization group invariance of the
two-loop effective potential, and compute the anomalous dimensions for scalars
and the beta function for the vacuum energy at two-loop order in softly broken
supersymmetry. Several illustrative examples and consistency checks are
included.Comment: 38 pages. Typos in equations (3.5), (3.11), and (6.3) are fixed.
Explicit claim of renormalization group invariance in the general case of
softly-broken supersymmetry is added. Additional discussion of cases of
multiple simple or U(1) groups. Equations in Appendix B rewritten in a more
useful for
Chiral symmetry breaking in gauged model in curved spacetime
Using the renormalization group (RG) approach and the equivalency between the
class of gauge-Higgs-Yukawa models and the gauged Nambu-Jona-Lasinio (NJL)
model, we study the gauged NJL model in curved space-time. The behaviour of the
scalar-gravitational coupling constant in both theories is discussed.
The RG improved effective potential of gauged NJL model in curved spacetime is
found. The curvature at which chiral symmetry in the gauged NJL model is broken
is obtained explicitly in a remarkably simple form. The powerful RG improved
effective potential formalizm leads to the same results as ladder
Schwinger-Dyson equations which have not been formulated yet in curved
spacetime what opens new possibilities in the study of GUTs and NJL-like models
in curved spacetime
Nobeyama Cygnus-X Survey: Physical Properties of CO clumps in DR-6(W), DR-9 and DR-13S regions
Cygnus-X is considered a region of interest for high-energy astrophysics,
since the Cygnus OB2 association has been confirmed as a PeVatron in the Cygnus
cocoon. In this research note, we present new high-resolution (16'')
CO(J=10) and CO (J=10) observations
obtained with the Nobeyama 45-m radiotelescope, to complement the Nobeyama
Cygnus-X Survey. We discovered 19 new CO clumps associated with the
star-forming regions DR-6W, DR-9, and DR13S. We present the physical parameters
of these clumps, which are consistent with the neighboring covered regions. We
confirm the clumpy nature of these regions and of a filament located between
DR6 and DR6W. These results strongly suggest that star formation occurs in
these regions with clumps of sizes 10 pc, masses 10
M, and H densities of 10 cm.Comment: 8 pages, 3 Figures, 1 Table. https://pos.sissa.it/444/631/pd
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