1,662 research outputs found
Carbon dioxide capture from a cement manufacturing process
A process of manufacturing cement clinker is provided in which a clean supply of CO.sub.2 gas may be captured. The process also involves using an open loop conversion of CaO/MgO from a calciner to capture CO.sub.2 from combustion flue gases thereby forming CaCO.sub.3/CaMg(CO.sub.3).sub.2. The CaCO.sub.3/CaMg(CO.sub.3).sub.2 is then returned to the calciner where CO.sub.2 gas is evolved. The evolved CO.sub.2 gas, along with other evolved CO.sub.2 gases from the calciner are removed from the calciner. The reactants (CaO/MgO) are feed to a high temperature calciner for control of the clinker production composition
Existence of the Stark-Wannier quantum resonances
In this paper we prove the existence of the Stark-Wannier quantum resonances
for one-dimensional Schrodinger operators with smooth periodic potential and
small external homogeneous electric field. Such a result extends the existence
result previously obtained in the case of periodic potentials with a finite
number of open gaps.Comment: 30 pages, 1 figur
Many-body position operator in lattice fermionic systems with periodic boundary conditions
A total position operator in the position representation is derived for
lattice fermionic systems with periodic boundary conditions. The operator is
shown to be Hermitian, the generator of translations in momentum space, and its
time derivative is shown to correspond to the total current operator in a
periodic system. The operator is such that its moments can be calculated up to
any order. To demonstrate its utility finite size scaling is applied to the
Brinkman-Rice transition as well as metallic and insulating Gutzwiller
wavefunctions.Comment: to appear in Journal of Physics A: Mathematical and General
(reference will be added later
Breaking of the overall permutation symmetry in nonlinear optical susceptibilities of one-dimensional periodic dimerized Huckel model
Based on infinite one-dimensional single-electron periodic models of
trans-polyacetylene, we show analytically that the overall permutation symmetry
of nonlinear optical susceptibilities is, albeit preserved in the molecular
systems with only bound states, no longer generally held for the periodic
systems. The overall permutation symmetry breakdown provides a fairly natural
explanation to the widely observed large deviations of Kleinman symmetry for
periodic systems in off-resonant regions. Physical conditions to experimentally
test the overall permutation symmetry break are discussed.Comment: 7 pages, 1 figur
Nonlinear Magneto-Optical Response of - and -Wave Superconductors
The nonlinear magneto-optical response of - and -wave superconductors
is discussed. We carry out the symmetry analysis of the nonlinear
magneto-optical susceptibility in the superconducting state. Due to the surface
sensitivity of the nonlinear optical response for systems with bulk inversion
symmetry, we perform a group theoretical classification of the superconducting
order parameter close to a surface. For the first time, the mixing of singlet
and triplet pairing states induced by spin-orbit coupling is systematically
taken into account. We show that the interference of singlet and triplet
pairing states leads to an observable contribution of the nonlinear
magneto-optical Kerr effect. This effect is not only sensitive to the
anisotropy of the gap function but also to the symmetry itself. In view of the
current discussion of the order parameter symmetry of High-T
superconductors, results for a tetragonal system with bulk singlet pairing for
various pairing symmetries are discussed.Comment: 21 pages (REVTeX) with 8 figures (Postscript
Transport and the Order Parameter of Superconducting UPt3
We calculate the ultrasonic absorption and the thermal conductivity in the
superconducting state of UPt as functions of temperature and direction of
propagation and polarization. Two leading candidates for the superconducting
order parameter are considered: the and representations. Both
can fit the data except for the ultrasonic absorption in the phase. To do
that, it is necessary to suppose that the system has only a single domain, and
that must be chosen as the most favorable one. However, the theory
requires fine-tuning of parameters to fit the low temperature thermal
conductivity. Thus, transport data favor the theory. Measurements of
the thermal conductivity as a function of pressure at low temperature could
help to further distinguish the two theories.Comment: 7 pages, 4 figure
Absence of Meissner State and Robust Ferromagnetism in the Superconducting State of UCoGe: Possible Evidence of Spontaneous Vortex State
We report ac magnetic susceptibility and dc magnetization measurements on the
superconducting ferromagnet UCoGe (with superconducting and Curie temperatures
of ~K and ~K, respectively).
In the normal, ferromagnetic state (), the
magnetization curve exhibits a hysteresis loop similar to that of a regular
itinerant ferromagnet. Upon lowering the temperature below , the
spontaneous magnetization is unchanged, but the hysteresis is markedly
enhanced. Even deeply inside the superconducting state, ferromagnetism is not
completely shielded, and there is no Meissner region, a magnetic field region
of (a lower critical field). From these results, we suggest
that UCoGe is the first material in which ferromagnetism robustly survives in
the superconducting state and a spontaneous vortex state without the Meissner
state is realized.Comment: 5 pages, 4 figures, to be published in J. Phys. Soc. Jp
Odd Frequency Pairing in the Kondo Lattice
We discuss the possibility that heavy fermion superconductors involve
odd-frequency pairing of the kind first considered by Berezinskii. Using a toy
model for odd frequency triplet pairing in the Kondo lattice we are able to
examine key properties of this new type of paired state. To make progress
treating the strong constraint in the Kondo lattice model we use the
technical trick of a Majorana representation of the local moments, which
permits variational treatments of the model without a Gutzwiller approximation.
The simplest mean field theory involves the development of bound states between
the local moments and conduction electrons, characterized by a spinor order
parameter. We show that this state is a stable realization of odd frequency
triplet superconductivity with surfaces of gapless excitations whose spin and
charge coherence factors vanish linearly in the quasiparticle energy. A
NMR relaxation rate coexists with a linear specific heat. We discuss possible
extensions of our toy model to describe heavy fermion superconductivity.Comment: 67 page
model of superconducting UPt
The phase diagram of superconducting UPt is explained in a
Ginzburg-Landau theory starting from the hypothesis that the order parameter is
a pseudo-spin singlet which transforms according to the representation
of the point group. We show how to compute the positions of the phase
boundaries both when the applied field is in the basal plane and when it is
along the c-axis. The experimental phase diagrams as determined by longitudinal
sound velocity data can be fit using a single set of parameters. In particular
the crossing of the upper critical field curves for the two field directions
and the apparent isotropy of the phase diagram are reproduced. The former is a
result of the magnetic properties of UPt and their contribution to the free
energy in the superconducting state. The latter is a consequence of an
approximate particle-hole symmetry. Finally we extend the theory to finite
pressure and show that, in contrast to other models, the model
explains the observed pressure dependence of the phase boundaries.Comment: RevTex, 29 pages, 18 PostScript figures in a uuencoded, gzipped tar
file. PostScript version of paper, tar file of PostScript figures and
individual PostScript figures are also available via anonymous ftp at
ftp://nym.physics.wisc.edu/anonymou/papers/upt3
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