15,926 research outputs found
Quantum Phases of the Shastry-Sutherland Kondo Lattice: Implications for the Global Phase Diagram of Heavy Fermion Metals
Considerable recent theoretical and experimental efforts have been devoted to
the study of quantum criticality and novel phases of antiferromagnetic
heavy-fermion metals. In particular, quantum phase transitions have been
discovered in the compound YbPtPb. These developments have motivated us
to study the competition between the RKKY and Kondo interactions on the
Shastry-Sutherland lattice. We determine the zero-temperature phase diagram as
a function of magnetic frustration and Kondo coupling within a slave-fermion
approach. Pertinent phases include the Shastry-Sutherland valence bond solid
and heavy Fermi liquid. In the presence of antiferromagnetic order, our
zero-temperature phase diagram is remarkably similar to the global phase
diagram proposed earlier based on general grounds. We discuss the implications
of our results for the experiments on YbPtPb and other geometrically
frustrated heavy fermion compounds.Comment: 5 pages 4 figures - Supplementary Material 4 pages 6 figures. Updated
with published versio
Effective potential for composite operators and for an auxiliary scalar field in a Nambu-Jona-Lasinio model
We derive the effective potentials for composite operators in a
Nambu-Jona-Lasinio (NJL) model at zero and finite temperature and show that in
each case they are equivalent to the corresponding effective potentials based
on an auxiliary scalar field. The both effective potentials could lead to the
same possible spontaneous breaking and restoration of symmetries including
chiral symmetry if the momentum cutoff in the loop integrals is large enough,
and can be transformed to each other when the Schwinger-Dyson (SD) equation of
the dynamical fermion mass from the fermion-antifermion vacuum (or thermal)
condensates is used. The results also generally indicate that two effective
potentials with the same single order parameter but rather different
mathematical expressions can still be considered physically equivalent if the
SD equation corresponding to the extreme value conditions of the two potentials
have the same form.Comment: 7 pages, no figur
T-Shape Molecular Heat Pump
We report on the first molecular device of heat pump modeled by a T-shape
Frenkel-Kontorova lattice. The system is a three-terminal device with the
important feature that the heat can be pumped from the low-temperature region
to the high-temperature region through the third terminal. The pumping action
is achieved by applying a stochastic external force that periodically modulates
the atomic temperature. The temperature, the frequency and the system size
dependence of heat pump are briefly discussed.Comment: 6 figure
Torsion in Graph Homology
Khovanov homology for knots has generated a flurry of activity in the
topology community. This paper studies the Khovanov type cohomology for graphs
with a special attention to torsions. When the underlying algebra is
, we determine precisely those graphs whose cohomology
contains torsion. For a larger class of algebras, we show that torsion often
occurs. Our investigation of torsion led to other related general results. The
ideas of this paper could potentially be used to predict the Khovanov-Rozansky
homology of knots (in particular torus knots). We also predict
that our work is connected with Hochschild and Connes cyclic homology of
algebras.Comment: 45 pages, 20 figures, Fundamenta Mathematicae, 190, 2006, to appea
Determination of and Extraction of from Semileptonic Decays
By globally analyzing all existing measured branching fractions and partial
rates in different four momentum transfer-squared bins of decays, we obtain the product of the form factor and magnitude of
CKM matrix element to be . With this
product, we determine the semileptonic form factor
in conjunction with the value of
determined from the SM global fit. Alternately, with the product together with
the input of the form factor calculated in lattice QCD recently, we
extract , where the error is
still dominated by the uncertainty of the form factor calculated in lattice
QCD. Combining the
extracted from all existing measurements of decays and
together, we find the most
precisely determined to be , which improves
the accuracy of the PDG'2014 value by
Replica study of pinned bubble crystals
In higher Landau levels (), the ground state of the two-dimensional
electron gas in a strong perpendicular magnetic field evolves from a Wigner
crystal for small filling of the partially filled Landau level, into a
succession of bubble states with increasing number of guiding centers per
bubble as increases, to a modulated stripe state near . In
this work, we compute the frequency-dependent longitudinal conductivity of the Wigner and bubble crystal states in the presence
of disorder. We apply an elastic theory to the crystal states which is
characterized by a shear and a bulk modulus. We obtain both moduli from the
microscopic time-dependent Hartree-Fock approximation. We then use the replica
and Gaussian variational methods to handle the effects of disorder. Within the
semiclassical approximation we get the dynamical conductivity as well as the
pinning frequency as functions of the Landau level filling factor and compare
our results with recent microwave experiments.Comment: 19 pages and 6 eps figure
THE STRUCTURE OF HUMAN ACHILLES TENDON AND ITS BIOMECHANICAL SIGNIFICANCE
The morphological characteristics, particularly the rotation structure, of human Achilles tendon were investigated on 21 I lower limb specimens 101 Achilles tendons of male adult specimens were measured The structure, function and biomechanical properties of the tendon, as well as inter-individual differences in tendon rotation and morphological indicators of tendon injury have been discussed The tendon fibers of two muscle groups (gastrocnemius and soleus) intersect each other in a rotating manner. This rotation is from medial to lateral The rotation starts at 12-15 cm above the calcaneum but becomes most obvious at approximately 5 cm above h e calcaneum. The degrees of rotation vary in every body and were divided into 3 types: light, medium and heavy. The percentage of h e 3 types of rotation are 58.29f 3.39, 3270f 3.23,9.01f 1.86, respectively. No significant deferences were found between two distinct sexes, sides, age-groups or races. The tendon length, upper-width,lower-widthand lower-thickness of adult Chinese males are 19.77f 0.246.58f 0.18, I.5Of Q04,0.68f 0.01 cm, respectively. The tendon rotation structure has some biomechanical implications for he tendon's adaptation lo the tremendous tractive forces developed during special situations Along with common factors known to result in tendon injury, we believe structural weakness to be one of the most important factors resulting in tendon injury. Common weaknesses in morphological structure are: the most avascular part of the tendon (approx. 44 cm above insertion), which is the most obvious position of rotation; the presence of a large number of Type 111 collagen in the tendon; he light rotation pattern of this tendon among the great majority of human beings; and the damage caused by Le saw-like action between h e two parts of tendon fibers In addition, owing to the two-joint (knee and ankle) spanning of the gastrocnemius, a stretched tendon will develop even greater tension and easily tear when the quadriceps muscle group contracts strongly during knee extension
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