295 research outputs found
Nucleon-nucleon scattering within a multiple subtractive renormalization approach
A methodology to renormalize the nucleon-nucleon interaction, using a
recursive multiple subtraction approach to construct the kernel of the
scattering equation, is presented. We solve the subtracted scattering equation
with the next-leading-order (NLO) and next-to-next-leading-order (NNLO)
interactions. The results are presented for all partial waves up to ,
fitted to low-energy experimental data. In our renormalizaton group invariant
method, when introducing the NLO and NNLO interactions, the subtraction energy
emerges as a renormalization scale and the momentum associated with it comes to
be about the QCD scale (), irrespectively to the partial wave.Comment: Final versio
Bethe-Salpeter bound-state structure in Minkowski space
The quantitative investigation of the scalar Bethe-Salpeter equation in
Minkowski space, within the ladder-approximation framework, is extended to
include the excited states. This study has been carried out for an interacting
system composed by two massive bosons exchanging a massive scalar, by adopting
(i) the Nakanishi integral representation of the Bethe-Salpeter amplitude, and
(ii) the formally exact projection onto the null plane. Our analysis, on one
hand, confirms the reliability of the method already applied to the ground
state and, on the other one, extends the investigation from the valence
distribution in momentum space to the corresponding quantity in the
impact-parameter space, pointing out some relevant features, like (i) the
equivalence between Minkowski and Euclidean transverse-momentum amplitudes, and
(ii) the leading exponential fall-off of the valence wave function in the
impact-parameter space.Comment: 15 pages, 7 figure
Quasi-bound states in continuum
We report the prediction of quasi-bound states (resonant states with very
long lifetimes) that occur in the eigenvalue continuum of propagating states
for a wide region of parameter space. These quasi-bound states are generated in
a quantum wire with two channels and an adatom, when the energy bands of the
two channels overlap. A would-be bound state that lays just below the upper
energy band is slightly destabilized by the lower energy band and thereby
becomes a resonant state with a very long lifetime (a second QBIC lays above
the lower energy band).Comment: 4 pages, 4figures, 1 tabl
Matter-wave 2D solitons in crossed linear and nonlinear optical lattices
It is demonstrated the existence of multidimensional matter-wave solitons in
a crossed optical lattice (OL) with linear OL in the direction and
nonlinear OL (NOL) in the direction, where the NOL can be generated by a
periodic spatial modulation of the scattering length using an optically induced
Feshbach resonance. In particular, we show that such crossed linear and
nonlinear OL allows to stabilize two-dimensional (2D) solitons against decay or
collapse for both attractive and repulsive interactions. The solutions for the
soliton stability are investigated analytically, by using a multi-Gaussian
variational approach (VA), with the Vakhitov-Kolokolov (VK) necessary criterion
for stability; and numerically, by using the relaxation method and direct
numerical time integrations of the Gross-Pitaevskii equation (GPE). Very good
agreement of the results corresponding to both treatments is observed.Comment: 8 pages (two-column format), with 16 eps-files of 4 figure
Controlled targeting of different subcellular sites by porphyrins in tumour-bearing mice.
Unilamellar liposomes of dipalmitoyl-phosphatidylcholine can incorporate various porphyrins in either the phospholipid bilayer or the internal aqueous compartment depending on the water-/lipo-solubility of the drug. Intraperitoneal injection of the liposome-bound porphyrins to mice bearing a MS-2 fibrosarcoma results in remarkably more efficient tumour targeting than that obtained by administration of the same porphyrins dissolved in homogeneous aqueous solution. Moreover, also water-insoluble porphyrins can be transported to the tumour via liposomes. Fractionation of liver and neoplastic cells indicates that the subcellular distribution of liposome-delivered porphyrins is also dependent on their solubility properties: thus, relatively polar porphyrins, such as tetra(4-sulfonatophenyl)porphine and uroporphyrin, are mainly recovered from the soluble fraction, whereas hydrophobic porphyrins, such as haematoporphyrin or porphyrin esters, preferentially partition in the cytoplasmic membrane. As a consequence, different subcellular sites can be targeted by porphyrins and possibly photodamaged through a suitable choice of the drug-carrier system
Analysis of a fluvial groynes system on hydraulic scale model
River morphodynamics and sediment transportSediment-structure interactio
Effect of nearest- and next-nearest neighbor interactions on the spin-wave velocity of one-dimensional quarter-filled spin-density-wave conductors
We study spin fluctuations in quarter-filled one-dimensional
spin-density-wave systems in presence of short-range Coulomb interactions. By
applying a path integral method, the spin-wave velocity is calculated as a
function of on-site (U), nearest (V) and next-nearest (V_2) neighbor-site
interactions. With increasing V or V_2, the pure spin-density-wave state
evolves into a state with coexisting spin- and charge-density waves. The
spin-wave velocity is reduced when several density waves coexist in the ground
state, and may even vanish at large V. The effect of dimerization along the
chain is also considered.Comment: REVTeX, 11 pages, 9 figure
Role of Collective Mode for Optical Conductivity and Reflectivity in Quarter-Filled Spin-Density-Wave State
Taking account of a collective mode relevant to charge fluctuation, the
optical conductivity of spin-density-wave state has been examined for an
extended Hubbard model with one-dimensional quarter-filled band. We find that,
within the random phase approximation, the conductivity exhibits several peaks
at the frequency corresponding to the excitation energy of the commensurate
collective mode. When charge ordering appears with increasing inter-site
repulsive interactions, the main peak with the lowest frequency is reduced and
the effective mass of the mode is enhanced indicating the suppression of the
effect of the collective mode by charge ordering. It is also shown that the
reflectivity becomes large in a wide range of frequency due to the huge
dielectric constant induced by the collective mode.Comment: 11 pages, 16 figure
Possible Metastable State Triggered by Competition of Peierls State and Charge Ordered State
We examine a Peierls ground state and its competing metastable state in the
one-dimensional quarter-filled Peierls-Hubbard model with the nearest-neighbor
repulsive interaction V and the electron-phonon interaction (\propto 1/K with K
being the elastic constant). From the mean-field approach, we obtain the phase
diagram for the ground state on the plane of parameters V and K. The coexistent
state of the spin-density wave and the charge ordering is realized for large V
and K. With decreasing K, it exhibits a first-order phase transition to the
unconventional Peierls state which is described by the bond-centered
charge-density-wave state. In the large region of the Peierls ground state in
the phase diagram, there exists the metastable state where the energy takes a
local minimum with respect to the lattice distortion. On the basis of the
present calculation, we discuss the photoinduced phase observed in the
(EDO-TTF)_{2}PF_{6} compound.Comment: 8 pages, 9 figure
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