6,083 research outputs found
(D+1)-Dimensional Formulation for D-Dimensional Constrained Systems
D-dimensional constrained systems are studied with stochastic Lagrangian
and\break Hamiltonian. It is shown that stochastic consistency conditions are
second class constraints and Lagrange multiplier fields can be determined in
(D+1)-dimensional canonical formulation. The Langevin equations for the
constrained system are obtained as Hamilton's equations of motion where
conjugate momenta play a part of noise fields.Comment: 10 pages (Plain TeX), CHIBA-EP-58-Re
Dynamical Symmetry Breaking on Langevin Equation : Nambu Jona-Lasinio Model
In order to investigate dynamical symmetry breaking, we study
NambuJona-Lasinio model in the large-N limit in the stochastic
quantization method. Here in order to solve Langevin equation, we impose
specified initial conditions and construct ``effective Langevin equation'' in
the large-N limit and give the same non-perturbative results as path-integral
approach gives. Moreover we discuss stability of vacuum by means of ``effective
potential''.Comment: 12 pages (Plain TeX), 7 figures(not included, sorry!), CHIBA-EP-6
Specific Heat and Superfluid Density for Possible Two Different Superconducting States in NaxCoO2.yH2O
Several thermodynamic measurements for the cobaltate superconductor,
NaxCoO2.yH2O, have so far provided results inconsistent with each other. In
order to solve the discrepancies, we microscopically calculate the temperature
dependences of specific heat and superfluid density for this superconductor. We
show that two distinct specific-heat data from Oeschler et al. and Jin et al.
are reproduced, respectively, for the extended s-wave state and the p-wave
state. Two different superfluid-density data are also reproduced for each case.
These support our recent proposal of possible two different pairing states in
this material. In addition, we discuss the experimentally proposed large
residual Sommerfeld coefficient and extremely huge effective carrier mass.Comment: 5 pages, 4 figures, Submitted to J. Phys. Soc. Jp
Fulde-Ferrell-Larkin-Ovchinnikov State in the absence of a Magnetic Field
We propose that in a system with pocket Fermi surfaces, a pairing state with
a finite total momentum q_tot like the Fulde-Ferrell-Larkin-Ovchinnikov state
can be stabilized even without a magnetic field. When a pair is composed of
electrons on a pocket Fermi surface whose center is not located at Gamma point,
the pair inevitably has finite q_tot. To investigate this possibility, we
consider a two-orbital model on a square lattice that can realize pocket Fermi
surfaces and we apply fluctuation exchange approximation. Then, by changing the
electron number n per site, we indeed find that such superconducting states
with finite q_tot are stabilized when the system has pocket Fermi surfaces.Comment: 4 pages, 5 figure
Sub-Cycle Optical Response Caused by Dressed State with Phase-Locked Wavefunctions
The coherent interaction of light with matter imprints the phase information
of the light field on the wavefunction of the photon-dressed electronic state.
Driving electric field, together with a stable phase that is associated with
the optical probe pulses, enables the role of the dressed state in the optical
response to be investigated. We observed optical absorption strengths modulated
on a sub-cycle timescale in a GaAs quantum well in the presence of a
multi-cycle terahertz driving pulse using a near-infrared probe pulse. The
measurements were in good agreement with the analytical formula that accounts
for the optical susceptibilities caused by the dressed state of excitons, which
indicates that the output probe intensity was coherently reshaped by the
excitonic sideband emissions
CoO2-Layer-Thickness Dependence of Magnetic Properties and Possible Two Different Superconducting States in NaxCoO2.yH2O
In order to understand the experimentally proposed phase diagrams of
NaxCoO2.yH2O, we theoretically study the CoO2-layer-thickness dependence of
magnetic and superconducting (SC) properties by analyzing a multiorbital
Hubbard model using the random phase approximation. When the Co valence (s) is
+3.4, we show that the magnetic fluctuation exhibits strong layer-thickness
dependence where it is enhanced at finite (zero) momentum in the thicker
(thinner) layer system. A magnetic order phase appears sandwiched by two SC
phases, consistent with the experiments. These two SC phases have different
pairing states where one is the singlet extended s-wave state and the other is
the triplet p-wave state. On the other hand, only a triplet p-wave SC phase
with dome-shaped behavior of Tc is predicted when s=+3.5, which is also
consistent with the experiments. Controversial experimental results on the
magnetic properties are also discussed.Comment: 5 pages, 4 figures. Submitted to Journal of the Physical Society of
Japa
Live imaging of whole mouse embryos during gastrulation : migration analyses of epiblast and mesodermal cells
During gastrulation in the mouse embryo, dynamic cell movements including epiblast invagination and mesodermal layer expansion lead to the establishment of the three-layered body plan. The precise details of these movements, however, are sometimes elusive, because of the limitations in live imaging. To overcome this problem, we developed techniques to enable observation of living mouse embryos with digital scanned light sheet microscope (DSLM). The achieved deep and high time-resolution images of GFP-expressing nuclei and following 3D tracking analysis revealed the following findings: (i) Interkinetic nuclear migration (INM) occurs in the epiblast at embryonic day (E)6 and 6.5. (ii) INM-like migration occurs in the E5.5 embryo, when the epiblast is a monolayer and not yet pseudostratified. (iii) Primary driving force for INM at E6.5 is not pressure from neighboring nuclei. (iv) Mesodermal cells migrate not as a sheet but as individual cells without coordination
Ideal Timing of Starting Weight-Bearing After Calcaneal Insufficiency Fracture: A Case Report and Review of the Literature
Introduction: Criteria for starting weight-bearing on the heel with a symptomatic calcaneal insufficiency fracture have not yet been reported.
Case Presentation: We describe a rare case of a 52-year-old woman with a calcaneal insufficiency fracture who sustained a second ipsilateral calcaneal insufficiency fracture within a short time span. The initial fracture was not evident radiographically, but was detected using magnetic resonance imaging (MRI). The patient rejected our advice to avoid weight-bearing on the heel, instead opting to use a silicone heel orthosis. Although there were no abnormal local findings, the stand on heel test was positive at each subsequent visit until 2 months after her first medical examination. At this time, radiographs showed a sclerotic line; however, a second round of MRI showed a new calcaneal insufficiency fracture anterior to the initial calcaneal insufficiency fracture. The patient then agreed to stop weight-bearing on the heel. Three months after the initial visit, radiographs showed two sclerotic lines, and the stand on heel test became negative for the first time; hence, weight-bearing was permitted. There was radiographic evidence of fracture healing and complete resolution of symptoms 4 months after the initial visit.
Conclusions: The callus formation seen on radiographs is helpful in determining when to start weight-bearing; however, fresh insufficiency fractures of the ipsilateral calcaneus may not be detected by radiography. Since local findings such as tenderness, swelling, and heat are subjective, the criteria for starting weight-bearing on the affected heel with an insufficiency fracture should be based on not only radiographs but also objective clinical findings such as the stand on heel test
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