1,089 research outputs found
Forward Electron-Phonon Scattering and HTS
Tunneling and point contact spectroscopy show clear phonon features and
together with optic measurements give strong support that the electron-phonon
interaction (EPI) is large in HTS oxides. Strong correlations in HTS oxides
renormalize the EPI (and interaction with impurities) so that the forward
scattering peak (FSP) develops for small hole doping \delta<<1. The FSP
mechanism explains important properties of the normal and superconducting
state.Comment: 6 pages, 5 figure
Baryogenesis, 30 Years after
A review of the basic principles of baryogenesis is given. Baryogenesis in
heavy particle decays as well as electroweak, SUSY-condensate, and spontaneous
baryogenesis are discussed. The models of abundant creation of antimatter in
the universe are briefly reviewed.Comment: 30 pages, latex twic
Conventional Superconductivity in Fe-Based Pnictides: the Relevance of Intra-Band Electron-Boson Scattering
Various recent experimental data and especially the large Fe-isotope effect
point against unconventional pairings, since the large intra-band impurity
scattering is strongly pair-breaking for them. The strength of the inter-band
impurity scattering in some single crystals may be strong and probably beyond
the Born scattering limit. In that case the proposed s(+-) pairing (hole(h)-
and electron(el)-gaps are of opposite signs) is suppressed but possibly not
completely destroyed. The data imply that the intra-band pairing in the h- and
in the el-band, which are inevitably due to some nonmagnetic el-boson
interaction (EBI), must be taken into account. EBI is either due to phonons
(EPI) or possibly due to excitons (EEI), or both are simultaneously operative.
We discuss their interplay briefly. The large Fe-isotope effect favors the EPI
and the s(+) pairing (the h- and el-gaps are in-phase).Comment: 7 pages, no figures, explanations and argumentations improved,
references adde
Jeans Instability in Classical and Modified Gravity
Gravitational instability in classical Jeans theory, General Relativity, and
modified gravity is considered. The background density increase leads to a
faster growth of perturbations in comparison with the standard theory. The
transition to the Newtonian gauge in the case of coordinate dependent
background metric functions is studied. For modified gravity a new high
frequency stable solution is found
Curvature Oscillations in Modified Gravity and High Energy Cosmic Rays
It is shown that F(R)-modified gravitational theories lead to curvature
oscillations in astrophysical systems with rising energy density. The frequency
and the amplitude of such oscillations could be very high and would lead to
noticeable production of energetic cosmic ray particles.Comment: 7 pages, 2 figures, author's affiliation is correcte
Bosonic Spectral Function and The Electron-Phonon Interaction in HTSC Cuprates
In Part I we discuss accumulating experimental evidence related to the
structure and origin of the bosonic spectral function in high-temperature
superconducting (HTSC) cuprates at and near optimal doping. Some global
properties of the spectral function, such as number and positions of peaks, are
extracted by combining optics, neutron scattering, ARPES and tunnelling
measurements. These methods give convincing evidence for strong electron-phonon
interaction (EPI) with the coupling constant between 1-3 in cuprates near
optimal doping. Here we clarify how these results are in favor of the
Eliashberg-like theory for HTSC cuprates near optimal doping. In Part II we
discuss some theoretical ingredients - such as strong EPI, strong correlations
- which are necessary to explain the experimental results related to the
mechanism of d-wave pairing in optimally doped cuprates. These comprise the
Migdal-Eliashberg theory for EPI in strongly correlated systems which give rise
to the forward scattering peak. The latter is further supported by the weakly
screened Madelung interaction in the ionic-metallic structure of layered
cuprates. In this approach EPI is responsible for the strength of pairing while
the residual Coulomb interaction (by including spin fluctuations) triggers the
d-wave pairing.Comment: 59 pages, 38 figures, review articl
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