17 research outputs found
Quantum origin of the early inflationary Universe
We give a detailed presentation of a recently proposed mechanism of
generating the energy scale of inflation by loop effects in quantum cosmology.
We discuss the quantum origin of the early inflationary Universe from the
no-boundary and tunneling quantum states and present a universal effective
action algorithm for the distribution function of chaotic inflationary
cosmologies in both of these states. The energy scale of inflation is
calculated by finding a sharp probability peak in this distribution function
for a tunneling model driven by the inflaton field with large negative constant
of non-minimal interaction. The sub-Planckian parameters of this peak
(the mean value of the corresponding Hubble constant , its
quantum width and the number of inflationary
e-foldings ) are found to be in good correspondence with the
observational status of inflation theory, provided the coupling constants of
the theory are constrained by a condition which is likely to be enforced by the
(quasi) supersymmetric nature of the sub-Planckian particle physics model.Comment: 43 pages, LaTeX, figures not include
Euclidean Maxwell theory in the presence of boundaries. II
zeta-function regularization is applied to complete a recent analysis of the quantized
electromagnetic field in the presence of boundaries. The quantum theory is studied by setting to
zero on the boundary the magnetic field, the gauge averaging functional. and hence the Faddeev-
Popov ghost field. Electric boundary conditions are also studied. On considering two gauge
functionals which involve covariant derivatives of the 4-vector potential, a series of detailed
calculations shows that, in the case of flaf Euclidean 4-space bounded by two concentric 3-
spheres, one-loop quantum amplitudes are gauge independent and their mode-by-mode evaluation
agrees with the covariant formulae for such amplitudes and coincides for magnetic or electric
boundary conditions. By contrast, if a single 3-sphere boundary is studied, one finds some
inconsistencies, i.e. gauge dependence of the amplitudes
Relativistic gauge conditions in quantum cosmology
This paper studies the quantization of the electromagnetic field
on a flat Euclidean background with boundaries. One-loop scaling
factors are evaluated for the one-boundary and two-boundary
backgrounds. The mode-by-mode analysis of Faddeev-Popov quantum
amplitudes is performed by using zeta-function regularization,
and is compared with the space-time covariant evaluation of the
same amplitudes. It is shown that a particular gauge condition
exists for which the corresponding operator matrix acting on
gauge modes is in diagonal form from the beginning. Moreover,
various relativistic gauge conditions are studied
in detail, to investigate the gauge invariance of the perturbative
quantum theory
Gravitons in one-loop quantum cosmology: correspondence between covariant and noncovariant formalisms
The discrepancy between the results of
covariant and noncovariant one-loop calculations for higher-spin
fields in quantum cosmology is analyzed.
A detailed mode-by-mode study of perturbative quantum gravity
about a flat Euclidean background bounded by two concentric
three-spheres, including nonphysical degrees of freedom and
ghost modes, leads to one-loop amplitudes in agreement with
the covariant Schwinger-DeWitt method. This calculation provides
the generalization of a previous analysis of fermionic fields
and electromagnetic fields at one-loop about flat Euclidean
backgrounds admitting a well-defined 3+1 decomposition
One-loop amplitudes in Euclidean quantum gravity
This paper studies the linearized
gravitational field in the presence of boundaries. For this
purpose, zeta-function regularization is used to perform the
mode-by-mode evaluation of BRST-invariant Faddeev-Popov
amplitudes in the case of flat Euclidean four-space
bounded by a three-sphere. On choosing the de Donder
gauge-averaging term, the resulting zeta(0) value is found
to agree with the space-time covariant calculation of the same
amplitudes, which relies on the recently corrected geometric
formulas for the asymptotic heat kernel in the case of mixed
boundary conditions. Two sets of mixed boundary conditions
for Euclidean quantum gravity are then compared in detail.
The analysis proves that one cannot restrict the
path-integral measure to transverse-traceless perturbations.
By contrast, gauge-invariant amplitudes are only obtained
on considering from the beginning all perturbative modes
of the gravitational field, jointly with ghost modes
Identification of complex core-shell nanostructures from the radial distributions of the local density of components
The paper is devoted to the substantiation and further development of the approach to the analysis of the mesoscopic and integral structure of binary metal nanoparticles from the radial distributions of the local density of the components. As an example, the local density distributions of Ni and Al obtained using the results of molecular dynamics modeling of binary Ni-Al nanoparticles with an initial uniform distribution of components and Ni@Al core-shell icosahedral nanostructures are considered. Both patterns demonstrate the surface segregation of Al atoms during relaxation and subsequent quenching of the initial configurations containing 5000 atoms in 1:1 ratio (nanoparticle radius 3 nm). During cooling, the temperature of the nanoparticles decreased from 1000 K to 0,01 K with a low for atomistic simulation cooling rate. Experimentally binary Ni-Al nanoparticles with a radius of about 100 nm (76Ni:24Al at.%) were synthesized by the wire electric explosion. The experimental intensity distributions obtained from the data of energy-dispersive analysis under the action of an electron beam are presented and analyzed. These distributions correspond to a greater extent to the initial configurations in our molecular dynamics experiments, i.e., they are obviously nonequilibrium. At the same time, it was concluded that the final molecular dynamic configurations are also not entirely equilibrium
Spin-3/2 potentials in backgrounds with boundary
This paper studies the two-spinor form of the
Rarita-Schwinger potentials subject to local boundary conditions
compatible with local supersymmetry.
The massless Rarita-Schwinger field equations are studied in
four-real-dimensional Riemannian backgrounds with boundary. Gauge
transformations on the potentials are shown to be compatible
with the field equations providing the background is Ricci-flat,
in agreement with previous results in the literature.
However, the preservation of boundary conditions under such
gauge transformations leads to a restriction of the gauge freedom.
The recent construction
by Penrose of secondary potentials which supplement the
Rarita-Schwinger potentials is then applied.
The equations for the secondary potentials, jointly with
the boundary conditions,
imply that the background four-geometry is further
restricted to be totally flat. The analysis of other gauge
transformations confirms that, in the massless case, the
only admissible class of Riemannian backgrounds with
boundary is totally flat
Water purification from chlorobenzenes using heteroatom functionalized carbon nanofibers produced on self organizing Ni Pd catalyst
The development of effective methods for the processing of hazardous wastes containing chlorinated hydrocarbons still remains a big challenge. Herein, the approach allowing the transformation of chlorohydrocarbons into functionalized carbon nanomaterials was demonstrated for 1,2 dichloroethane DCE used as a model compound. Carbon nanofibers CNF doped with nitrogen and oxygen heteroatoms were fabricated by a joint decomposition of DCE and co reagent CH3CN, NH4OH, C2H5OH, and H2O . The Ni Pd 5 alloy was used as a catalyst precursor for the CNF synthesis. Pristine Ni Pd alloy was found to undergo disintegration under the reaction conditions and to induce an active growth of the functionalized carbon nanofibers. The obtained CNF were shown to have a similar segmental structure of carbon filaments and to possess high specific surface area up to 470 m2 g and porosity up to 0.9 cm3 g . According to X ray photoelectron spectroscopy data, the nitrogen content within CNF samples prepared using N comprising precursors was about 1.0 1.7 at . The total oxygen content reaches 3.6 at . The obtained materials were demonstrated to be attractive for the dichlorobenzene adsorption from its aqueous solution