17,262 research outputs found
Lagrangian approach to local symmetries and self-dual model in gauge invariant formulation
Taking the St\"uckelberg Lagrangian associated with the abelian self-dual
model of P.K. Townsend et al as a starting point, we embed this mixed first-
and second-class system into a pure first-class system by following
systematically the generalized Hamiltonian approach of Batalin, Fradkin and
Tyutin. The resulting Lagrangian possesses an extended gauge invariance and
provides a non-trivial example for a general Lagrangian approach to unravelling
the full set of local symmetries of a Lagrangian.Comment: LaTeX, 15 page
Electronic Structure of Pyrochlore Iridates: From Topological Dirac Metal to Mott Insulator
In 5d transition metal oxides such as the iridates, novel properties arise
from the interplay of electron correlations and spin-orbit interactions. We
investigate the electronic structure of the pyrochlore iridates, (such as
YIrO) using density functional theory, LDA+U method, and
effective low energy models. A remarkably rich phase diagram emerges on tuning
the correlation strength U. The Ir magnetic moment are always found to be
non-collinearly ordered. However, the ground state changes from a magnetic
metal at weak U, to a Mott insulator at large U. Most interestingly, the
intermediate U regime is found to be a Dirac semi-metal, with vanishing density
of states at the Fermi energy. It also exhibits topological properties -
manifested by special surface states in the form of Fermi arcs, that connect
the bulk Dirac points. This Dirac phase, a three dimensional analog of
graphene, is proposed as the ground state of YIrO and related
compounds. A narrow window of magnetic `axion' insulator, with axion parameter
, may also be present at intermediate U. An applied magnetic field
induces ferromagnetic order and a metallic ground state.Comment: 7pages + 2pages appendices. 7 figures; see also viewpoint article by
L. Balents, "Weyl Electrons Kiss", at Physics 4, 36 (2011
Energy transfer, pressure tensor and heating of kinetic plasma
Kinetic plasma turbulence cascade spans multiple scales ranging from
macroscopic fluid flow to sub-electron scales. Mechanisms that dissipate large
scale energy, terminate the inertial range cascade and convert kinetic energy
into heat are hotly debated. Here we revisit these puzzles using fully kinetic
simulation. By performing scale-dependent spatial filtering on the Vlasov
equation, we extract information at prescribed scales and introduce several
energy transfer functions. This approach allows highly inhomogeneous energy
cascade to be quantified as it proceeds down to kinetic scales. The pressure
work, , can
trigger a channel of the energy conversion between fluid flow and random
motions, which is a collision-free generalization of the viscous dissipation in
collisional fluid. Both the energy transfer and the pressure work are strongly
correlated with velocity gradients.Comment: 28 pages, 10 figure
Quantization of spontaneously broken gauge theory based on the BFT-BFV Formalism
We quantize the spontaneously broken abelian U(1) Higgs model by using the
improved BFT and BFV formalisms. We have constructed the BFT physical fields,
and obtain the first class observables including the Hamiltonian in terms of
these fields. We have also explicitly shown that there are exact form
invariances between the second class and first class quantities. Then,
according to the BFV formalism, we have derived the corresponding Lagrangian
having U(1) gauge symmetry. We also discuss at the classical level how one
easily gets the first class Lagrangian from the symmetry-broken second class
Lagrangian.Comment: 16 pages, latex, final version published in Mod. Phys. Lett.
Calculated Momentum Dependence of Zhang-Rice States in Transition Metal Oxides
Using a combination of local density functional theory and cluster exact
diagonalization based dynamical mean field theory, we calculate many body
electronic structures of several Mott insulating oxides including undoped high
T_{c} materials. The dispersions of the lowest occupied electronic states are
associated with the Zhang-Rice singlets in cuprates and with doublets,
triplets, quadruplets and quintets in more general cases. Our results agree
with angle resolved photoemission experiments including the decrease of the
spectral weight of the Zhang--Rice band as it approaches k=0
Searching for Dark Matter Signals in the Left-Right Symmetric Gauge Model with CP Symmetry
We investigate singlet scalar dark matter (DM) candidate in a left-right
symmetric gauge model with two Higgs bidoublets (2HBDM) in which the
stabilization of the DM particle is induced by the discrete symmetries P and
CP. According to the observed DM abundance, we predict the DM direct and
indirect detection cross sections for the DM mass range from 10 GeV to 500 GeV.
We show that the DM indirect detection cross section is not sensitive to the
light Higgs mixing and Yukawa couplings except the resonance regions. The
predicted spin-independent DM-nucleon elastic scattering cross section is found
to be significantly dependent on the above two factors. Our results show that
the future DM direct search experiments can cover the most parts of the allowed
parameter space. The PAMELA antiproton data can only exclude two very narrow
regions in the 2HBDM. It is very difficult to detect the DM direct or indirect
signals in the resonance regions due to the Breit-Wigner resonance effect.Comment: 24 pages, 8 figures. minor changes and a reference added, published
in Phys. Rev.
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