2,456,056 research outputs found
Renormalization Group Study of the Electron-phonon Interaction in the High Tc Cuprates
We generalize the numerical renormalization group scheme to study the
phonon-mediated retarded interactions in the high Tc cuprates. We find that
three sets of phonon-mediated retarded quasiparticle scatterings grow under RG
flow. These scatterings share the following common features: 1) the initial and
final quasiparticle momenta are in the antinodal regions, and 2) the scattering
amplitudes have a symmetry. All three sets of retarded interaction
are driven to strong coupling by the magnetic fluctuations around .
After growing strong, these retarded interaction will trigger density wave
orders with d-wave symmetry. However, due to the d-wave form factor they will
leave the nodal quasiparticle unaffected. We conclude that the main effect of
electron-phonon coupling in the cuprates is to promote these density wave
orders.Comment: 4 pages, 3 figures, references added, added more details about
others' previous studie
A Method of Areas for Manipulating the Entanglement Properties of One Copy of a Two-Particle Pure State
We consider the problem of how to manipulate the entanglement properties of a
general two-particle pure state, shared between Alice and Bob, by using only
local operations at each end and classical communication between Alice and Bob.
A method is developed in which this type of problem is found to be equivalent
to a problem involving the cutting and pasting of certain shapes along with a
certain colouring problem. We consider two problems. Firstly we find the most
general way of manipulating the state to obtain maximally entangled states.
After such a manipulation the entangled state |11>+|22>+....|mm> is obtained
with probability p_m. We obtain an expression for the optimal average
entanglement. Also, some results of Lo and Popescu pertaining to this problem
are given simple geometric proofs. Secondly, we consider how to manipulate one
two particle entangled pure state to another with certainty. We derive
Nielsen's theorem (which states the necessary and sufficient condition for this
to be possible) using the method of areas.Comment: 29 pages, 9 figures. Section 2.4 clarified. Error in second colouring
theorem (section 3.2) corrected. Some other minor change
Determinations of |V_ub| and |V_cb| from measurements of B -> X_u,c\ell\nu differential decay rates
Methods are described in the framework of light-cone expansion which allow
one to determine the Cabibbo-Kobayashi-Maskawa matrix elements |V_ub| and
|V_cb| from measurements of the differential decay rates as a function of the
scaling variables in the inclusive semileptonic decays of B mesons. By these
model-independent methods the dominant hadronic uncertainties can be avoided
and the B -> X_u\ell\nu decay can be very efficiently differentiated from the B
-> X_c\ell\nu decay, which may lead to precise determinations of |V_ub| and
|V_cb|.Comment: 11 pages, 2 figures, version as published in Mod. Phys. Lett. A, more
discussion, references added, title chang
Binding between endohedral Na atoms in Si clathrate I; a first principles study
We investigate the binding nature of the endohedral sodium atoms with the
ensity functional theory methods, presuming that the clathrate I consists of a
sheaf of one-dimensional connections of Na@Si cages interleaved in three
perpendicular directions. Each sodium atom loses 30% of the 3s charge to
the frame, forming an ionic bond with the cage atoms; the rest of the electron
contributes to the covalent bond between the nearest Na atoms. The presumption
is proved to be valid; the configuration of the two Na atoms in the nearest
Si cages is more stable by 0.189 eV than that in the Si and
Si cages. The energy of the beads of the two distorted Na atoms is more
stable by 0.104 eV than that of the two infinitely separated Na atoms. The
covalent bond explains both the preferential occupancies in the Si cages
and the low anisotropic displacement parameters of the endohedral atoms in the
Si cages in the [100] directions of the clathrate I.Comment: First page: Affiliation added to PDF and PS versio
Turbulence and turbulent mixing in natural fluids
Turbulence and turbulent mixing in natural fluids begins with big bang
turbulence powered by spinning combustible combinations of Planck particles and
Planck antiparticles. Particle prograde accretions on a spinning pair releases
42% of the particle rest mass energy to produce more fuel for turbulent
combustion. Negative viscous stresses and negative turbulence stresses work
against gravity, extracting mass-energy and space-time from the vacuum.
Turbulence mixes cooling temperatures until strong-force viscous stresses
freeze out turbulent mixing patterns as the first fossil turbulence. Cosmic
microwave background temperature anisotropies show big bang turbulence fossils
along with fossils of weak plasma turbulence triggered as plasma photon-viscous
forces permit gravitational fragmentation on supercluster to galaxy mass
scales. Turbulent morphologies and viscous-turbulent lengths appear as linear
gas-proto-galaxy-clusters in the Hubble ultra-deep-field at z~7. Proto-galaxies
fragment into Jeans-mass-clumps of primordial-gas-planets at decoupling: the
dark matter of galaxies. Shortly after the plasma to gas transition,
planet-mergers produce stars that explode on overfeeding to fertilize and
distribute the first life.Comment: 23 pages 12 figures, Turbulent Mixing and Beyond 2009 International
Center for Theoretical Physics conference, Trieste, Italy. Revision according
to Referee comments. Accepted for Physica Scripta Topical Issue to be
published in 201
Fault tolerant quantum key distribution protocol with collective random unitary noise
We propose an easy implementable prepare-and-measure protocol for robust
quantum key distribution with photon polarization. The protocol is fault
tolerant against collective random unitary channel noise. The protocol does not
need any collective quantum measurement or quantum memory. A security proof and
a specific linear optical realization using spontaneous parametric down
conversion are given.Comment: Accepted by PRA as a Rapid Communicatio
Eavesdropping without quantum memory
In quantum cryptography the optimal eavesdropping strategy requires that the
eavesdropper uses quantum memories in order to optimize her information. What
happens if the eavesdropper has no quantum memory? It is shown that the best
strategy is actually to adopt the simple intercept/resend strategy.Comment: 9 pages LaTeX, 3 figure
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