14,411 research outputs found
Correlation Functions in Two-Dimensional Dilaton Gravity
The Liouville approach is applied to the quantum treatment of the dilaton
gravity in two dimensions. The physical states are obtained from the BRST
cohomology and correlation functions are computed up to three-point functions.
For the case (i.e., without matter), the cosmological term operator is
found to have the discrete momentum that plays a special role in the
Liouville gravity. The correlation functions for arbitrary numbers of operators
are found in the case, and are nonvanishing only for specific
``chirality'' configurations.Comment: 14 pages, TIT/HEP-204, STUPP-92-13
Field-induced long-range order in the S=1 antiferromagnetic chain
The quasi-one dimensional S=1 antiferromagnet in magnetic field H is
investigated with the exact diagonalization of finite chains and the mean field
approximation for the interchain interaction. In the presence of the single-ion
anisotropy D, the full phase diagram in the plane is presented for H
\parallel D and H \perp D. The shape of the field-induced long-range ordered
phase is revealed to be quite different between the two cases, as observed in
the recent experiment of NDMAP. The estimated ratio of the interchain and
intrachain couplings of NDMAP (J'/J ~ 10^{-3}) is consistent with the neutron
scattering measurement.Comment: 4 pages, Revtex, with 6 eps figure
Quantum Chromodynamics with Many Flavors
We investigate the phase structure of lattice QCD for general number of
flavors . Based on numerical data combined with the results of the
perturbation theory we propose the following picture: When , there
is only one IR fixed point at vanishing gauge coupling, i.e., the theory in the
continuum limit is trivial. On the other hand, when , there
is a non-trivial fixed point. Therefore, the theory is non-trivial with
anomalous dimensions, however, without quark confinement. Theories which
satisfy both quark confinement and spontaneous chiral symmetry breaking in the
continuum limit exist only for .Comment: Talk presented by K. Kanaya at the 1997 Yukawa International Seminar
(YKIS'97) on ``Non-Perturbative QCD --- Structure of the QCD Vacuum ---'',
YITP, Kyoto, Japan, 2--12 Dec. 1997. To be published in the proceedings
[Prog. Theor. Phys. Suppl.
Penrose Limit and Six-Dimensional Gauge Theories
We study the Penrose limit of the (p,q) fivebranes supergravity background. We consider the different phases of the worldvolume field theory and their weakly coupled descriptions. In the Penrose limit we get a solvable string theory and compute the spectrum. It corresponds to states of the six-dimensional worldvolume theory with large energy and large U(1) charge. We comment on the RG behavior of the gauge theory
Single domain YBCO/Ag bulk superconductors fabricated by seeded infiltration and growth
We have applied the seeded infiltration and growth (IG) technique to the processing of samples containing Ag in an attempt to fabricate Ag-doped Y-Ba-Cu-O (YBCO) bulk superconductors with enhanced mechanical properties. The IG technique has been used successfully to grow bulk Ag-doped YBCO superconductors of up to 25 mm in diameter in the form of single grains. The distribution of Ag in the parent Y-123 matrix fabricated by the IG technique is observed to be at least as uniform as that in samples grown by conventional top seeded melt growth (TSMG). Fine Y-211 particles were observed to be embedded within the Y-123 matrix for the IG processed samples, leading to a high critical current density, Jc, of over 70 kA/cm2 at 77.3 K in self-field. The distribution of Y-211 in the IG sample microstructure, however, is inhomogeneous, which leads to a variation in the spatial distribution of Jc throughout the bulk matrix. A maximum-trapped field of around 0.43 T at 1.2 mm above the sample surface (i.e. including 0.7 mm for the sensor mould thickness) is observed at liquid nitrogen temperature, despite the relatively small grain size of the sample (20 mm diameter × 7 mm thickness)
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