1,608 research outputs found
Anomalous behaviors of the charge and spin degrees of freedom in the CuO double chains of PrBaCuO
The density-matrix renormalization-group method is used to study the
electronic states of a two-chain Hubbard model for CuO double chains of
PrBaCuO. We show that the model at quarter filling has the charge
ordered phases with stripe-type and in-line--type patterns in the parameter
space, and in-between, there appears a wide region of vanishing charge gap; the
latter phase is characteristic of either Tomonaga-Luttinger liquid or a
metallic state with a spin gap. We argue that the low-energy electronic state
of the CuO double chains of PrBaCuO should be in the metallic state
with a possibly small spin gap.Comment: REVTEX 4, 10 pages, 9 figures; submitted to PR
Effect of oil upon lime mortar
Thesis (BS)--University of Illinois, 1893MsBound with: Brown, Frank M Ratio of window area to floor area of buildings IU-
Pyrochlore Antiferromagnet: A Three-Dimensional Quantum Spin Liquid
The quantum pyrochlore antiferromagnet is studied by perturbative expansions
and exact diagonalization of small clusters. We find that the ground state is a
spin-liquid state: The spin-spin correlation functions decay exponentially with
distance and the correlation length never exceeds the interatomic distance. The
calculated magnetic neutron diffraction cross section is in very good agreement
with experiments performed on Y(Sc)Mn2. The low energy excitations are
singlet-singlet ones, with a finite spin gap.Comment: 4 pages, 4 figure
Hubbard chains network on corner-sharing tetrahedra: origin of the heavy fermion state in LiV_2O_4
We investigate the Hubbard chains network model defined on corner-sharing
tetrahedra (the pyrochlore lattice) which is a possible microscopic model for
the heavy fermion state of LiV_2O_4. Based upon this model, we can explain
transport, magnetic, and thermodynamic properties of LiV_2O_4. We calculate the
spin susceptibility, and the specific heat coefficient, exploiting the Bethe
ansatz exact solution of the 1D Hubbard model and bosonization method. The
results are quite consistent with experimental observations. We obtain the
large specific heat coefficient .Comment: 5 pages, 2 figures, a postscript file of Figure 1 is not included, to
appear in Physical Review
Buffer gas induced collision shift for the Sr clock transition
Precision saturation spectroscopy of the is
performed in a vapor cell filled with various rare gas including He, Ne, Ar,
and Xe. By continuously calibrating the absolute frequency of the probe laser,
buffer gas induced collision shifts of kHz are detected with gas
pressure of 1-20 mTorr. Helium gave the largest fractional shift of . Comparing with a simple impact calculation and a
Doppler-limited experiment of Holtgrave and Wolf [Phys. Rev. A {\bf 72}, 012711
(2005)], our results show larger broadening and smaller shifting coefficient,
indicating effective atomic loss due to velocity changing collisions. The
applicability of the result to the optical lattice clock
transition is also discussed
Bessel bridges decomposition with varying dimension. Applications to finance
We consider a class of stochastic processes containing the classical and
well-studied class of Squared Bessel processes. Our model, however, allows the
dimension be a function of the time. We first give some classical results in a
larger context where a time-varying drift term can be added. Then in the
non-drifted case we extend many results already proven in the case of classical
Bessel processes to our context. Our deepest result is a decomposition of the
Bridge process associated to this generalized squared Bessel process, much
similar to the much celebrated result of J. Pitman and M. Yor. On a more
practical point of view, we give a methodology to compute the Laplace transform
of additive functionals of our process and the associated bridge. This permits
in particular to get directly access to the joint distribution of the value at
t of the process and its integral. We finally give some financial applications
to illustrate the panel of applications of our results
Pressure Induced Quantum Critical Point and Non-Fermi-Liquid Behavior in BaVS3
The phase diagram of BaVS3 is studied under pressure using resistivity
measurements. The temperature of the metal to nonmagnetic Mott insulator
transition decreases under pressure, and vanishes at the quantum critical point
p_cr=20kbar. We find two kinds of anomalous conducting states. The
high-pressure metallic phase is a non-Fermi liquid described by Delta rho = T^n
where n=1.2-1.3 at 1K < T < 60K. At p<p_cr, the transition is preceded by a
wide precursor region with critically increasing resistivity which we ascribe
to the opening of a soft Coulomb gap.Comment: 4 pages, 5 eps figures, problem with figure correcte
Itinerant-Electron Magnet of the Pyrochlore Lattice: Indium-Doped YMn2Zn20
We report on a ternary intermetallic compound, "YMn2Zn20", comprising a
pyrochlore lattice made of Mn atoms. A series of In-doped single crystals
undergo no magnetic long-range order down to 0.4 K, in spite of the fact that
the Mn atom carries a local magnetic moment at high temperatures, showing
Curie-Weiss magnetism. However, In-rich crystals exhibit spin-glass transitions
at approximately 10 K due to a disorder arising from the substitution, while,
with decreasing In content, the spin-glass transition temperature is reduced to
1 K. Then, heat capacity divided by temperature approaches a large value of 280
mJ K-2 mol-1, suggesting a significantly large mass enhancement for conduction
electrons. This heavy-fermion-like behavior is not induced by the Kondo effect
as in ordinary f-electron compounds, but by an alternative mechanism related to
the geometrical frustration on the pyrochlore lattice, as in (Y,Sc)Mn2 and
LiV2O4, which may allow spin entropy to survive down to low temperatures and to
couple with conduction electrons.Comment: 5 pages, 4 figures, J. Phys. Soc. Jpn., in pres
Circadian Organization in Hemimetabolous Insects
The circadian system of hemimetabolous insects is reviewed in respect to the locus of the circadian clock and multioscillatory organization. Because of relatively easy access to the nervous system, the neuronal organization of the clock system in hemimetabolous insects has been studied, yielding identification of the compound eye as the major photoreceptor for entrainment and the optic lobe for the circadian clock locus. The clock site within the optic lobe is inconsistent among reported species; in cockroaches the lobula was previously thought to be a most likely clock locus but accessory medulla is recently stressed to be a clock center, while more distal part of the optic lobe including the lamina and the outer medulla area for the cricket. Identification of the clock cells needs further critical studies. Although each optic lobe clock seems functionally identical, in respect to photic entrainment and generation of the rhythm, the bilaterally paired clocks form a functional unit. They interact to produce a stable time structure within individual insects by exchanging photic and temporal information through neural pathways, in which
serotonin and pigment-dispersing factor (PDF) are involved as chemical messengers. The mutual interaction also plays an important role in seasonal adaptation of the rhythm
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