7,408 research outputs found
Properties of scalar perturbations generated by conformal scalar field
Primordial scalar perturbations may be generated when complex conformal
scalar field rolls down its negative quartic potential. We begin with the
discussion of peculiar infrared properties of this scenario. We then consider
the statistical anisotropy inherent in the model. Finally, we discuss the
non-Gaussianity of scalar perturbations. Because of symmetries, the bispectrum
vanishes identically. We present a general expression for the trispectrum and
give its explicit form in the folded limit.Comment: Prepared for "Gravity and Cosmology (GC2010)" workshop, Kyoto, Japan,
May,24-July,16, 2010; 15 pages, 1 figur
Non-Gaussianity of scalar perturbations generated by conformal mechanisms
We consider theories which explain the flatness of the power spectrum of
scalar perturbations in the Universe by conformal invariance, such as conformal
rolling model and Galilean Genesis. We show that to the leading {\it
non-linear} order, perturbations in all models from this class behave in one
and the same way, at least if the energy density of the relevant fields is
small compared to the total energy density (spectator approximation). We then
turn to the intrinsic non-Gaussianities in these models (as opposed to
non-Gaussianities that may be generated during subsequent evolution). The
intrinsic bispectrum vanishes, so we perform the complete calculation of the
trispectrum and compare it with the trispecta of local forms in various limits.
The most peculiar feature of our trispectrum is a (fairly mild) singularity in
the limit where two momenta are equal in absolute value and opposite in
direction (folded limit). Generically, the intrinsic non-Gaussianity can be of
detectable size.Comment: 28 pages, 5 figures. Journal version. A comment on the size of the
non-Gaussianities inserted. Misprints corrected. A reference adde
Octonic Electrodynamics
In this paper we present eight-component values "octons", generating
associative noncommutative algebra. It is shown that the electromagnetic field
in a vacuum can be described by a generalized octonic equation, which leads
both to the wave equations for potentials and fields and to the system of
Maxwell's equations. The octonic algebra allows one to perform compact combined
calculations simultaneously with scalars, vectors, pseudoscalars and
pseudovectors. Examples of such calculations are demonstrated by deriving the
relations for energy, momentum and Lorentz invariants of the electromagnetic
field. The generalized octonic equation for electromagnetic field in a matter
is formulated.Comment: 12 pages, 1 figur
Nanopattern-stimulated superconductor-insulator transition in thin TiN films
We present the results of the comparative study of the influence of disorder
on transport properties in continuous and nanoperforated TiN films. We show
that nanopatterning turns a thin TiN film into an array of superconducting weak
links and stimulates both, the disorder- and magnetic field-driven
superconductor-to-insulator transitions, pushing them to lower degree of
disorder. We find that nanopatterning enhances the role of the two-dimensional
Coulomb interaction in the system transforming the originally insulating film
into a more pronounced insulator. We observe magnetoresistance oscillations
reflecting collective behaviour of the multiconnected nanopatterned
superconducting film in the wide range of temperatures and uncover the physical
mechanism of these oscillations as phase slips in superconducting weak link
network.Comment: 6 pages, 4 figure
On some algebraic examples of Frobenius manifolds
We construct some explicit quasihomogeneous algebraic solutions to the
associativity (WDVV) equations by using analytical methods of the finite gap
integration theory. These solutions are expanded in the uniform way to
non-semisimple Frobenius manifolds.Comment: 14 page
Parafermionic Liouville field theory and instantons on ALE spaces
In this paper we study the correspondence between the
coset conformal field
theories and SU(n) gauge theories on
. Namely we check the correspondence between the
SU(2) Nekrasov partition function on and the
conformal blocks of the parafermion algebra (in and modules).
We find that they are equal up to the U(1)-factor as it was in all cases of
AGT-like relations. Studying the structure of the instanton partition function
on we also find some evidence that this
correspondence with arbitrary takes place up to the U(1)-factor.Comment: 21 pages, 6 figures, misprints corrected, references added, version
to appear in JHE
A New Feather Mite Species of the Genus \u3ci\u3eTrouessartia\u3c/i\u3e Canestrini (Acariformes: Trouessartiidae) from the Northern Rough-winged Swallow \u3ci\u3eStelgidopteryx serripennis\u3c/i\u3e (Passeriformes: Hirundinidae) in Pennsylvania
A new feather mite species, Trouessartia stelgidopteryx sp. n. (Astigmata: Trouessartiidae), is described from the Northern rough-winged swallow Stelgidopteryx serripennis Newton (Passeriformes: Hirundinidae) in Pennsylvania, USA. The new species is close to the minutipes species group and differs from its representatives and all other known species of the genus Trouessartia in having a unique combination of features in males: the opisthosomal lobes are much longer than wide, they are separated by a large semi-ovate terminal cleft, and their lobar apices bear semi-ovate terminal lamellae with a smooth margin
Determination of local scours near platforms at Piltun-Astohskoye and Lunskoye oil and gas field during joined action of waves and currents
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