2,144 research outputs found
Experimental evidence for new symmetry axis of electromagnetic beams
The new symmetry axis of a well-behaved electromagnetic beam advanced in
paper Physical Review A 78, 063831 (2008) is not purely a mathematical concept.
The experimental result reported by Hosten and Kwiat in paper Science 319, 787
(2008) is shown to demonstrate the existence of this symmetry axis that is
neither perpendicular nor parallel to the propagation axis.Comment: 10 pages and 3 figure
Field theory of massive and massless vector particles in the Duffin - Kemmer - Petiau formalism
Field theory of massive and massless vector particles is considered in the
first-order formalism. The Hamiltonian form of equations is obtained after the
exclusion of non-dynamical components. We obtain the canonical and symmetrical
Belinfante energy-momentum tensors and their nonzero traces. We note that the
dilatation symmetry is broken in the massive case but in the massless case the
modified dilatation current is conserved. The canonical quantization is
performed and the propagator of the massive fields is found in the Duffin -
Kemmer - Petiau formalism.Comment: 20 pages, typos corrected, a reference added, journal version,
accepted in Int.J.Mod.Phys.
Solutions of Podolsky's Electrodynamics Equation in the First-Order Formalism
The Podolsky generalized electrodynamics with higher derivatives is
formulated in the first-order formalism. The first-order relativistic wave
equation in the 20-dimensional matrix form is derived. We prove that the
matrices of the equation obey the Petiau-Duffin-Kemmer algebra. The
Hermitianizing matrix and Lagrangian in the first-order formalism are given.
The projection operators extracting solutions of field equations for states
with definite energy-momentum and spin projections are obtained, and we find
the density matrix for the massive state. The -matrix Schrodinger
form of the equation is derived, and the Hamiltonian is obtained. Projection
operators extracting the physical eigenvalues of the Hamiltonian are found.Comment: 17 pages, minor corrections, published versio
Cosmic ray modulation in a random anisotropic magnetic field
Inhomogeneities of the interplanetary magnetic field can be divided into small scale and large scale ones as may be required by the character of the problem of cosmic ray (CR) propagation. CR propagation in stochastic magnetic fields is of diffusion character. The main contribution into the scattering of CR particles is made by their interaction with inhomogeneities of the magnetic field H which have characteristic dimensions 1 of the order of Larmor radius R=cp/eH of particle (p is the absolute value of particle momentum, e is particle charge, c is velocity of light). Scattering of particles on such inhomogeneities leads to their diffusion mostly along a magnetic field with characteristic dimensions of variation in space exceeding the mean free path
Kalb-Ramond fields in the Petiau-Duffin-Kemmer formalism and scale invariance
Kalb-Ramond equations for massive and massless particles are considered in
the framework of the Petiau-Duffin-Kemmer formalism. We obtain
matrices of the relativistic wave equation of the first-order and solutions in
the form of density matrix. The canonical and Belinfante energy-momentum
tensors are found. We investigate the scale invariance and obtain the conserved
dilatation current. It was demonstrated that the conformal symmetry is broken
even for massless fields.Comment: 9 pages, no figure
On calculating the Berry curvature of Bloch electrons using the KKR method
We propose and implement a particularly effective method for calculating the
Berry curvature arising from adiabatic evolution of Bloch states in wave vector
k space. The method exploits a unique feature of the Korringa-Kohn-Rostoker
(KKR) approach to solve the Schr\"odinger or Dirac equations. Namely, it is
based on the observation that in the KKR method k enters the calculation via
the structure constants which depend only on the geometry of the lattice but
not the crystal potential. For both the Abelian and non-Abelian Berry curvature
we derive an analytic formula whose evaluation does not require any numerical
differentiation with respect to k. We present explicit calculations for Al, Cu,
Au, and Pt bulk crystals.Comment: 13 pages, 5 figure
Spectral and polarization effects in deterministically nonperiodic multilayers containing optically anisotropic and gyrotropic materials
Influence of material anisotropy and gyrotropy on optical properties of
fractal multilayer nanostructures is theoretically investigated. Gyrotropy is
found to uniformly rotate the output polarization for bi-isotropic multilayers
of arbitrary geometrical structure without any changes in transmission spectra.
When introduced in a polarization splitter based on a birefringent fractal
multilayer, isotropic gyrotropy is found to resonantly alter output
polarizations without shifting of transmission peak frequencies. The design of
frequency-selective absorptionless polarizers for polarization-sensitive
integrated optics is outlined
Local Phonon Density of States in an Elastic Substrate
The local, eigenfunction-weighted acoustic phonon density of states (DOS)
tensor is calculated for a model substrate consisting of a semi-infinite
isotropic elastic continuum with a stress-free surface. On the surface, the
local DOS is proportional to the square of the frequency, as for the
three-dimensional Debye model, but with a constant of proportionality that is
considerably enhanced compared to the Debye value, a consequence of the
Rayleigh surface modes. The local DOS tensor at the surface is also
anisotropic, as expected. Inside the substrate the local DOS is both spatially
anisotropic and non-quadratic in frequency. However, at large depths, the local
DOS approaches the isotropic Debye value. The results are applied to a Si
substrate.Comment: 7 pages, 2 figures, RevTe
The Effective Fragment Molecular Orbital Method for Fragments Connected by Covalent Bonds
We extend the effective fragment molecular orbital method (EFMO) into
treating fragments connected by covalent bonds. The accuracy of EFMO is
compared to FMO and conventional ab initio electronic structure methods for
polypeptides including proteins. Errors in energy for RHF and MP2 are within 2
kcal/mol for neutral polypeptides and 6 kcal/mol for charged polypeptides
similar to FMO but obtained two to five times faster. For proteins, the errors
are also within a few kcal/mol of the FMO results. We developed both the RHF
and MP2 gradient for EFMO. Compared to ab initio, the EFMO optimized structures
had an RMSD of 0.40 and 0.44 {\AA} for RHF and MP2, respectively.Comment: Revised manuscrip
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