18,312 research outputs found
An optimal gap theorem
By solving the Cauchy problem for the Hodge-Laplace heat equation for
-closed, positive -forms, we prove an optimal gap theorem for
K\"ahler manifolds with nonnegative bisectional curvature which asserts that
the manifold is flat if the average of the scalar curvature over balls of
radius centered at any fixed point is a function of .
Furthermore via a relative monotonicity estimate we obtain a stronger
statement, namely a `positive mass' type result, asserting that if is
not flat, then for any
Non-minimal coupling of photons and axions
We establish a new self-consistent system of equations accounting for a
non-minimal interaction of gravitational, electromagnetic and axion fields. The
procedure is based on a non-minimal extension of the standard
Einstein-Maxwell-axion action. The general properties of a ten-parameter family
of non-minimal linear models are discussed. We apply this theory to the models
with pp-wave symmetry and consider propagation of electromagnetic waves
non-minimally coupled to the gravitational and axion fields. We focus on exact
solutions of electrodynamic equations, which describe quasi-minimal and
non-minimal optical activity induced by the axion field. We also discuss
empirical constraints on coupling parameters from astrophysical birefringence
and polarization rotation observations.Comment: 31 pages, 2 Tables; replaced with the final version published in
Classical and Quantum Gravit
Extended axion electrodynamics: Optical activity induced by nonstationary dark matter
We establish a new self-consistent Einstein-Maxwell-axion model based on the
Lagrangian, which is linear in the pseudoscalar (axion) field and its
four-gradient and includes the four-vector of macroscopic velocity of the axion
system as a whole. We consider extended equations of the axion electrodynamics,
modified gravity field equations, and discuss nonstationary effects in the
phenomenon of optical activity induced by axions.Comment: 6 pages, 0 figures, accepted for publication in the Journal
Gravitation and Cosmology, reported at the 14th Russian Gravitational
Conference (Ulyanovsk, 2011
Transition from Mott insulator to superconductor in GaNbSe and GaTaSe under high pressure
Electronic conduction in GaMSe (M=Nb;Ta) compounds with the fcc
GaMoS-type structure originates from hopping of localized unpaired
electrons (S=1/2) among widely separated tetrahedral M metal clusters. We
show that under pressure these systems transform from Mott insulators to a
metallic and superconducting state with T=2.9 and 5.8K at 13 and 11.5GPa
for GaNbSe and GaTaSe, respectively. The occurrence of
superconductivity is shown to be connected with a pressure-induced decrease of
the MSe octahedral distortion and simultaneous softening of the phonon
associated with MSe-bonds.Comment: 10 pages, 5 figure
Non-ancient solution of the Ricci flow
For any complete noncompact Khler manifold with nonnegative and
bounded holomorphic bisectional curvature,we provide the necessary and
sufficient condition for non-ancient solution to the Ricci flow in this paper.Comment: seven pages, latex fil
PENGARUH “ SERING CETING ” TERHADAP PENGETAHUAN IBU BALITA TENTANG STUNTING
In East Kalimantan, prevalence of stunting was increasing from 26.7% in 2015 becomes 30.8% in 2018. In 2019 from 10 regencies in East Kalimantan, prevalence in Kutai Kartanegara Regency 19.49% and prevalence in Balikpapan City placed in second to reach 18.48%. Stunting affects cognitive and physic of children, productvity declines, bad health and high risk to degenerative diseases. Survey of this research said that 3 from 5 mothers who has stunting baby, has no knowladge of stunting and what stunting is, meanwhile knowladge significantly effect on prevention and treatment stunting. There is an inovation of transfer knowladge about stunting called “SerInG CeTing” which is unapplied in Health center of Baru Tengah so that the researcher want to analysis the effect of “SerInG CeTing”. This research used quasi eksperimen dengan one group pre-post test without control group design. Purpose of this research to influance analysis of “SerInG CeTing” on Mothers. The sampling technique used total sampling with 38 mothers who have stunting toddler in Health Center of Baru Tengah in Mei 2022. The result of this research “SerInG CeTing” is one of inovation which significanly increasing knowladge of mother in stunting with p value 0.000 < 0.05
Scattering of relativistic particles with Aharonov-Bohm-Coulomb interaction in two dimensions
The Aharonov-Bohm-Coulomb potentials in two dimensions may describe the
interaction between two particles carrying electric charge and magnetic flux,
say, Chern--Simons solitons, or so called anyons. The scattering problem for
such two-body systems is extended to the relativistic case, and the scattering
amplitude is obtained as a partial wave series. The electric charge and
magnetic flux is (, ) for one particle and (, ) for the
other. When , and takes on integer
or half integer values, the partial wave series is summed up approximately to
give a closed form. The results exhibit some nonperturbative features and
cannot be obtained from perturbative quantum electrodynamics at the tree level.Comment: revtex, 11 pages, no figur
New selection rules for resonant Raman scattering on quantum wires
The bosonisation technique is used to calculate the resonant Raman spectrum
of a quantum wire with two electronic sub-bands occupied. Close to resonance,
the cross section at frequencies in the region of the inter sub-band
transitions shows distinct peaks in parallel polarisation of the incident and
scattered light that are signature of collective higher order spin density
excitations. This is in striking contrast to the conventional selection rule
for non-resonant Raman scattering according to which spin modes can appear only
in perpendicular polarisation. We predict a new selection rule for the
excitations observed near resonance, namely that, apart from charge density
excitations, only spin modes with positive group velocities can appear as peaks
in the spectra in parallel configuration close to resonance. The results are
consistent with all of the presently available experimental data.Comment: 7 pages, 2 figure
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