8,915 research outputs found
Phenomenological Analysis of and Elastic Scattering Data in the Impact Parameter Space
We use an almost model-independent analytical parameterization for and
elastic scattering data to analyze the eikonal, profile, and
inelastic overlap functions in the impact parameter space. Error propagation in
the fit parameters allows estimations of uncertainty regions, improving the
geometrical description of the hadron-hadron interaction. Several predictions
are shown and, in particular, the prediction for inelastic overlap
function at TeV shows the saturation of the Froissart-Martin
bound at LHC energies.Comment: 15 pages, 16 figure
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Analytical treatments of micro-channel and micro-capillary flows
This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.Extensive work in the field of micro-channel and micro-capillary flows using the extended Navier-Stokes equations are carried out in this paper by taking the diffusive mass transport into account and provided the basis for analytical treatments of these flows. The results are compared with experimental results for micro-channels and showed good agreement. It is found that a characteristic pressure is useful to explain the comparisons. In addition, the work on micro-channel flows is extended to micro-capillary flows, to provide analytical treatments of this class of flows. The analytical results show similar behavior to that of micro-channel flows. Comparisons between the analytical results and experimental findings are also presented and discussed by introducing the characteristic pressure
Critical Collapse of an Ultrarelativistic Fluid in the Limit
In this paper we investigate the critical collapse of an ultrarelativistic
perfect fluid with the equation of state in the limit of
. We calculate the limiting continuously self similar (CSS)
solution and the limiting scaling exponent by exploiting self-similarity of the
solution. We also solve the complete set of equations governing the
gravitational collapse numerically for and
compare them with the CSS solutions. We also investigate the supercritical
regime and discuss the hypothesis of naked singularity formation in a generic
gravitational collapse. The numerical calculations make use of advanced methods
such as high resolution shock capturing evolution scheme for the matter
evolution, adaptive mesh refinement, and quadruple precision arithmetic. The
treatment of vacuum is also non standard. We were able to tune the critical
parameter up to 30 significant digits and to calculate the scaling exponents
accurately. The numerical results agree very well with those calculated using
the CSS ansatz. The analysis of the collapse in the supercritical regime
supports the hypothesis of the existence of naked singularities formed during a
generic gravitational collapse.Comment: 23 pages, 16 figures, revised version, added new results of
investigation of a supercritical collapse and the existence of naked
singularities in generic gravitational collaps
Boosting up quantum key distribution by learning statistics of practical single photon sources
We propose a simple quantum-key-distribution (QKD) scheme for practical
single photon sources (SPSs), which works even with a moderate suppression of
the second-order correlation of the source. The scheme utilizes a
passive preparation of a decoy state by monitoring a fraction of the signal via
an additional beam splitter and a detector at the sender's side to monitor
photon number splitting attacks. We show that the achievable distance increases
with the precision with which the sub-Poissonian tendency is confirmed in
higher photon number distribution of the source, rather than with actual
suppression of the multi-photon emission events. We present an example of the
secure key generation rate in the case of a poor SPS with , in
which no secure key is produced with the conventional QKD scheme, and show that
learning the photon-number distribution up to several numbers is sufficient for
achieving almost the same achievable distance as that of an ideal SPS.Comment: 11 pages, 3 figures; published version in New J. Phy
Eight-band calculations of strained InAs/GaAs quantum dots compared with one, four, and six-band approximations
The electronic structure of pyramidal shaped InAs/GaAs quantum dots is
calculated using an eight-band strain dependent Hamiltonian. The
influence of strain on band energies and the conduction-band effective mass are
examined. Single particle bound-state energies and exciton binding energies are
computed as functions of island size. The eight-band results are compared with
those for one, four and six bands, and with results from a one-band
approximation in which m(r) is determined by the local value of the strain. The
eight-band model predicts a lower ground state energy and a larger number of
excited states than the other approximations.Comment: 8 pages, 7 figures, revtex, eps
Evaporative Deposition Patterns Revisited: Spatial Dimensions of the Deposit
A model accounting for finite spatial dimensions of the deposit patterns in
the evaporating sessile drops of colloidal solution on a plane substrate is
proposed. The model is based on the assumption that the solute particles occupy
finite volume and hence these dimensions are of the steric origin. Within this
model, the geometrical characteristics of the deposition patterns are found as
functions of the initial concentration of the solute, the initial geometry of
the drop, and the time elapsed from the beginning of the drying process. The
model is solved analytically for small initial concentrations of the solute and
numerically for arbitrary initial concentrations of the solute. The agreement
between our theoretical results and the experimental data is demonstrated, and
it is shown that the observed dependence of the deposit dimensions on the
experimental parameters can indeed be attributed to the finite dimensions of
the solute particles. These results are universal and do not depend on any free
or fitting parameters; they are important for understanding the evaporative
deposition and may be useful for creating controlled deposition patterns.Comment: 34 pages, 14 figures, LaTeX; submitted to Physical Review
Calculation of pure dephasing for excitons in quantum dots
Pure dephasing of an exciton in a small quantum dot by optical and acoustic
phonons is calculated using the ``independent boson model''. Considering the
case of zero temperature the dephasing is shown to be only partial which
manifests itself in the polarization decaying to a finite value. Typical
dephasing times can be assigned even though the spectra exhibits strongly
non-Lorentzian line shapes. We show that the dephasing from LO phonon
scattering, occurs on a much larger time scale than that of dephasing due to
acoustic phonons which for low temperatures are also a more efficient dephasing
mechanism. The typical dephasing time is shown to strongly depend on the
quantum dot size whereas the electron phonon ``coupling strength'' and external
electric fields tend mostly to effect the residual coherence. The relevance of
the dephasing times for current quantum information processing implementation
schemes in quantum dots is discussed
Probing the d_{x2-y2}-wave Pomeranchuk instability by ultrasound
Selection rules of ultrasound attenuation and sound velocity renormalization
are analyzed in view of their potential application to identify Pomeranchuk
instabilities (electronic nematic phase). It is shown that the transverse sound
attenuation along [110] direction is enhanced by the Fermi surface fluctuations
near a d_{x2-y2}-wave Pomeranchuk instability, while the attenuation along
[100] direction remains unaffected. Moreover the fluctuation regime above the
instability is analyzed by means of a self-consistent renormalization scheme.
The results could be applied directly to Sr3Ru2O7 which is a potential
candidate for a Pomeranchuk instability at its metamagnetic transition in
strong magnetic fields.Comment: 14 pages, 12 figure
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