4,638 research outputs found
Canonical treatment of two dimensional gravity as an anomalous gauge theory
The extended phase space method of Batalin, Fradkin and Vilkovisky is applied
to formulate two dimensional gravity in a general class of gauges. A BRST
formulation of the light-cone gauge is presented to reveal the relationship
between the BRST symmetry and the origin of current algebra. From the
same principle we derive the conformal gauge action suggested by David, Distler
and Kawai.Comment: 11 pages, KANAZAWA-92-1
Multi-Bunch Solutions of Differential-Difference Equation for Traffic Flow
Newell-Whitham type car-following model with hyperbolic tangent optimal
velocity function in a one-lane circuit has a finite set of the exact solutions
for steady traveling wave, which expressed by elliptic theta function. Each
solution of the set describes a density wave with definite number of
car-bunches in the circuit. By the numerical simulation, we observe a
transition process from a uniform flow to the one-bunch analytic solution,
which seems to be an attractor of the system. In the process, the system shows
a series of cascade transitions visiting the configurations closely similar to
the higher multi-bunch solutions in the set.Comment: revtex, 7 pages, 5 figure
Twist Symmetry and Classical Solutions in Open String Field Theory
We construct classical solutions of open string field theory which are not
invariant under ordinary twist operation. From detailed analysis of the moduli
space of the solutions, it turns out that our solutions become nontrivial at
boundaries of the moduli space. The cohomology of the modified BRST operator
and the CSFT potential evaluated by the level truncation method strongly
support the fact that our nontrivial solutions correspond to the closed string
vacuum. We show that the nontrivial solutions are equivalent to the twist even
solution which was found by Takahashi and Tanimoto, and twist invariance of
open string field theory remains after the shift of the classical backgrounds.Comment: 19 pages, 2 figures; v2: errors fixe
Analysis of resonant inelastic x-ray scattering at the edge in NiO
We analyze the resonant inelastic x-ray scattering (RIXS) spectra at the Ni
edge in an antiferromagnetic insulator NiO by applying the theory developed
by the present authors. It is based on the Keldysh Green's function formalism,
and treats the core-hole potential in the intermediate state within the Born
approximation. We calculate the single-particle energy bands within the
Hartree-Fock approximation on the basis of the multi-orbital tight-binding
model. Using these energy bands together with the density of states from
an ab initio band structure calculation, we calculate the RIXS intensities as a
function of energy loss. By taking account of electron correlation within the
random phase approximation (RPA), we obtain quantitative agreement with the
experimental RIXS spectra, which consist of prominent two peaks around 5 eV and
8 eV, and the former shows considerable dispersion while the latter shows no
dispersion. We interpret the peaks as a result of a band-to-band transition
augmented by the RPA correlation.Comment: 11 pages, 10 figures, submitted to PR
Acute lower limb ischemia due to thrombo-embolic arterial occlusions in two previously healthy men with markedly elevated Lp(a)
Lipoprotein (a) (Lp(a)) is a well-documented risk factor for atherosclerotic cardiovascular disease. Its role in acute thrombo-embolic occlusions of peripheral arteries is not known. We describe two cases of multiple, acute, peripheral arterial occlusions in two previously healthy men with markedly elevated Lp(a). Both cases had unsatisfactory results after percutaneous and surgical revascularization procedures. Experience yielded in these two cases suggests that when an unfavorable outcome occurs in a peripheral artery disease patient in the absence of the regular risk factors, Lp(a) should be determined and its role investigated
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