4,128 research outputs found
Yang-Mills Magneto-Fluid Unification
We generalize the hybrid magneto-fluid model of a charged fluid interacting
with an electromagnetic field to the dynamics of a relativistic hot fluid
interacting with a non-Abelian field. The fluid itself is endowed with a
non-Abelian charge and the consequences of this generalization are worked out.
Applications of this formalism to the Quark Gluon Plasma are suggested.Comment: 6 pages, RevTex
BaV3O8: A possible Majumdar-Ghosh system with S=1/2
BaV3O8 contains both magnetic V4+(S=1/2) ions and non-magnetic V5+(S=0) ions.
The V4+ ions are arranged in a coupled Majumdar-Ghosh chain like network. Our
magnetic susceptibility chi(T) data fit well with the Curie-Weiss formula in
the temperature range of 80-300K and it yields a Curie constant
C=0.39cm3K/mole-V4+ and an antiferromagnetic Weiss temperature theta=-26K. The
chi(T) curve shows a broad maximum at T~25K indicative of short-range order
(SRO) and an anomaly corresponding to long-range order (LRO) at TN~6K. The
value of the frustration index (f=mod[theta/TN]~5) suggests that the system is
moderately frustrated. Above the LRO temperature the experimental magnetic
susceptibility data match well with the coupled Majumdar-Ghosh chain model with
the ratio of the nnn (next-nearest neighbor) to nn (nearest neighbor) magnetic
coupling alpha=2 and Jnnn/kB=40K. In a mean-field approach when considering the
inter-chain interactions, we obtain the total inter-chain coupling to be about
16K. The LRO anomaly at TN is also observe in the specific heat Cp(T) data and
is not sensitive to an applied magnetic field up to 90kOe. A 51V NMR signal
corresponding to the non-magnetic vanadium was observed. Anomalies at 6K were
observed in the variation with temperature of the 51V NMR linewidth and in the
spin-lattice relaxation rate 1/T1, indicating that they are sensitive to the
LRO onset and fluctuations at the magnetic V sites. The existence of two
components (one short and another long) is observed in the spin-spin relaxation
rate 1/T2 data in the vicinity of TN. The shorter component seems to be
intimately connected with the magnetically ordered state. We suggest that both
magnetically ordered and non-long range ordered (non-LRO) regions coexist in
this compound below the long range ordering temperature.Comment: Accepted in Phys. Rev.
Balancing Bounded Treewidth Circuits
Algorithmic tools for graphs of small treewidth are used to address questions
in complexity theory. For both arithmetic and Boolean circuits, it is shown
that any circuit of size and treewidth can be
simulated by a circuit of width and size , where , if , and otherwise. For our main construction,
we prove that multiplicatively disjoint arithmetic circuits of size
and treewidth can be simulated by bounded fan-in arithmetic formulas of
depth . From this we derive the analogous statement for
syntactically multilinear arithmetic circuits, which strengthens a theorem of
Mahajan and Rao. As another application, we derive that constant width
arithmetic circuits of size can be balanced to depth ,
provided certain restrictions are made on the use of iterated multiplication.
Also from our main construction, we derive that Boolean bounded fan-in circuits
of size and treewidth can be simulated by bounded fan-in
formulas of depth . This strengthens in the non-uniform setting
the known inclusion that . Finally, we apply our
construction to show that {\sc reachability} for directed graphs of bounded
treewidth is in
Investigating non-Fritzsch like texture specific quark mass matrices
A detailed investigation of all possible textures of Fritzsch-like and
non-Fritzsch like, 144 for texture 6 zero and 432 for texture 5 zero mass
matrices, have been carried out to ascertain their compatibility with the
existing quark mixing data. It seems that all the texture 6 zero possibilities
are completely ruled out whereas in the case of texture 5 zero mass matrices
the only viable possibility looks to be that of Fritzsch-like.Comment: 13 pages, 4 figures, Accepted for publication in IJMP
Quantum Monte Carlo study of a nonmagnetic impurity in the two-dimensional Hubbard model
In order to investigate the effects of nonmagnetic impurities in strongly
correlated systems, Quantum Monte Carlo (QMC) simulations have been carried out
for the doped two-dimensional Hubbard model with one nonmagnetic impurity.
Using a bare impurity potential which is onsite and attractive, magnetic and
single-particle properties have been calculated. The QMC results show that
giant oscillations develop in the Knight shift response around the impurity
site due to the short-range antiferromagnetic correlations. These results are
useful for interpreting the NMR data on Li and Zn substituted layered cuprates.Comment: 10 pages, 7 figure
The Relativistic Generalization of the Gravitational Force for Arbitrary Spacetimes
It has been suggested that re-expressing relativity in terms of forces could
provide fresh insights. The formalism developed for this purpose only applied
to static, or conformally static, space-times. Here we extend it to arbitrary
space-times. It is hoped that this formalism may lead to a workable definition
of mass and energy in relativity.Comment: 16 page
Spin-gap behaviour in the 2-leg spin-ladder BiCu2PO6
We present magnetic suscceptibility and heat capacity data on a new S=1/2
two-leg spin ladder compound BiCu2PO6. From our susceptibility analysis, we
find that the leg coupling J1/k_B is ~ 80 K and the ratio of the rung to leg
coupling J2/J1 ~ 0.9. We present the magnetic contribution to the heat capacity
of a two-leg ladder. The spin-gap Delta/k_B =3 4 K obtained from the heat
capacity agrees very well with that obtained from the magnetic susceptibility.
Significant inter-ladder coupling is suggested from the susceptibility
analysis. The hopping integrals determined using Nth order muffin tin orbital
(NMTO) based downfolding method lead to ratios of various exchange couplings in
agreement with our experimental data. Based on our band structure analysis, we
find the inter-ladder coupling in the bc-plane J2 to be about 0.75J1 placing
the compound presumably close to the quantum critical limit.Comment: 8 pages, 5 figure
31P NMR study of Na2CuP2O7: a S=1/2 two-dimensional Heisenberg antiferromagnetic system
The magnetic properties of Na2CuP2O7 were investigated by means of 31P
nuclear magnetic resonance (NMR), magnetic susceptibility, and heat capacity
measurements. We report the 31P NMR shift, the spin-lattice 1/T1, and spin-spin
1/T2 relaxation-rate data as a function of temperature T.
The temperature dependence of the NMR shift K(T) is well described by the
S=1/2 square lattice Heisenberg antiferromagnetic (HAF) model with an
intraplanar exchange of J/k_B \simeq 18\pm2 K and a hyperfine coupling A =
(3533\pm185) Oe/mu_B. The 31P NMR spectrum was found to broaden abruptly below
T \sim 10 K signifying some kind of transition. However, no anomaly was noticed
in the bulk susceptibility data down to 1.8 K. The heat capacity appears to
have a weak maximum around 10 K. With decrease in temperatures, the
spin-lattice relaxation rate 1/T1 decreases monotonically and appears to agree
well with the high temperature series expansion expression for a S = 1/2 2D
square lattice.Comment: 12 pages, 8 figures, submitted to J. Phys.: Cond. Ma
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