9,172 research outputs found
-kaon cross section in meson exchange model
We calculate the cross section for the dissociation of by kaons
within the framework of a meson exchange model including anomalous parity
interactions. Off-shell effects at the vertices were handled with QCD sum rule
estimates for the running coupling constants. The total -kaon cross
section was found to be mb for 4.1\leq\sqrt{s}\leq5 \GeV.Comment: 13 pages, 4 eps figure
Entanglement of an impurity and conduction spins in the Kondo model
Based on Yosida's ground state of the single-impurity Kondo Hamiltonian, we
study three kinds of entanglement between an impurity and conduction electron
spins. First, it is shown that the impurity spin is maximally entangled with
all the conduction electrons. Second, a two-spin density matrix of the impurity
spin and one conduction electron spin is given by a Werner state. We find that
the impurity spin is not entangled with one conduction electron spin even
within the Kondo screening length , although there is the spin-spin
correlation between them. Third, we show the density matrix of two conduction
electron spins is nearly same to that of a free electron gas. The single
impurity does not change the entanglement structure of the conduction electrons
in contrast to the dramatic change in electrical resistance.Comment: 5 pages, 2 figures, accepted for publication in Physical Review
Quantum Separability of Thermal Spin One Boson Systems
Using the temperature Green's function approach we investigate entanglement
between two non-interacting spin 1 bosons in thermal equilibrium. We show that,
contrary to the fermion case, the entanglement is absent in the spin density
matrix. Separability is demonstrated using the Peres-Horodecki criterion for
massless particles such as photons in black body radiation. For massive
particles, we show that the density matrix can be decomposed with separable
states.Comment: References & comments related to AQFT added. no figure, revtex4, to
be published in Phys. Lett.
Testing tripartite Mermin inequalities by spectral joint-measurements of qubits
It is well known that Bell inequality supporting the local realism can be
violated in quantum mechanics. Numerous tests of such a violation have been
demonstrated with bipartite entanglements. Using spectral jointmeasurements of
the qubits, we here propose a scheme to test the tripartite Mermin inequality
(a three-qubit Bell-type inequality) with three qubits dispersively-coupled to
a driven cavity. First, we show how to generate a three-qubit
Greenberger-Horne-Zeilinger (GHZ) state by only one-step quantum operation.
Then, spectral joint-measurements are introduced to directly confirm such a
tripartite entanglement. Assisted by a series of single-qubit operations, these
measurements are further utilized to test the Mermin inequality. The
feasibility of the proposal is robustly demonstrated by the present numerical
experiments.Comment: 7pages,3figure
Entanglement between qubits induced by a common environment with a gap
We study a system of two qubits interacting with a common environment,
described by a two-spin boson model. We demonstrate two competing roles of the
environment: inducing entanglement between the two qubits and making them
decoherent. For the environment of a single harmonic oscillator, if its
frequency is commensurate with the induced two-qubit coupling strength, the two
qubits could be maximally entangled and the environment could be separable. In
the case of the environment of a bosonic bath, the gap of its spectral density
function is essential to generate entanglement between two qubits at
equilibrium and for it to be used as a quantum data bus.Comment: accepted for publication in Physical Review
Charmonium - Pion Cross Section from QCD Sum Rules
The , and cross sections as a function of are evaluated in a QCD sum rule
calculation. We study the Borel sum rule for the four point function involving
pseudoscalar and vector meson currents, up to dimension four in the operator
product expansion. We find that our results are smaller than the cross sections obtained with models based on meson exchange,
but are close to those obtained with quark exchange models.Comment: revised version accepted for publication in Phys. Lett.
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Entropy and Efficiency of the ETF Market
We investigate the relative information efficiency of financial markets by measuring the entropy of the time series of high frequency data. Our tool to measure efficiency is the Shannon entropy, applied to 2-symbol and 3-symbol discretisations of the data. Analysing 1-min and 5-min price time series of 55 Exchange Traded Funds traded at the New York Stock Exchange, we develop a methodology to isolate residual inefficiencies from other sources of regularities, such as the intraday pattern, the volatility clustering and the microstructure effects. The first two are modelled as multiplicative factors, while the microstructure is modelled as an ARMA noise process. Following an analytical and empirical combined approach, we find a strong relationship between low entropy and high relative tick size and that volatility is responsible for the largest amount of regularity, averaging 62% of the total regularity against 18% of the intraday pattern regularity and 20% of the microstructure
and vertices in a QCD Sum Rule approach
We calculate the strong form factors and coupling constants of
and vertices using the QCD sum rules technique. In each case we
have considered two different cases for the off-shell particle in the vertex:
the ligthest meson and one of the heavy mesons. The method gives the same
coupling constant for each vertex. When the results for different vertices are
compared, they show that the SU(4) symmetry is broken by around 40%.Comment: 10 pages, 8 figures. Submitted to Phys. Lett.
Wavelength-swept Tm-doped fiber laser operating in the two-micron wavelength band
A wavelength-swept thulium-doped silica fiber laser using an intracavity rotating slotted-disk wavelength scanning filter in combination with an intracavity solid etalon for passive control of temporal and spectral profiles is reported. The laser yielded a wavelength swept output in a step-wise fashion with each laser pulse separated from the previous pulse by a frequency interval equal to the free-spectral-range of the etalon and with an instantaneous linewidth of <0.05 nm. Scanning ranges from 1905 nm to 2049 nm for a cladding-pumping laser configuration, and from 1768 nm to 1956 nm for a core-pumping laser configuration were achieved at average output powers up to ~1 W
Chiral Symmetry in Charmonium - Pion Cross Section
We perform a non-perturbative calculation of the cross section
using a effective Lagrangian. Our results differ from those
of previous calculations, specially in the description of vertices involving
pions.Comment: 6 pages, RevTeX including 2 figures in eps file
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