926 research outputs found
Density dependence of resonance broadening and shadowing effects in nuclear photoabsorption
Medium effects as a function of the mass number are studied in the total
photonuclear cross section from the -resonance region up to the region
where shadowing effects are known to exist. A consistent picture is obtained by
simply assuming a density dependence of the different mechanisms of resonance
broadening and shadowing. The -mass shift is found to increase with
.Comment: 7 pages, LaTeX, 2 figures available from the author
Quantum parallel dense coding of optical images
We propose quantum dense coding protocol for optical images. This protocol
extends the earlier proposed dense coding scheme for continuous variables
[S.L.Braunstein and H.J.Kimble, Phys.Rev.A 61, 042302 (2000)] to an essentially
multimode in space and time optical quantum communication channel. This new
scheme allows, in particular, for parallel dense coding of non-stationary
optical images. Similar to some other quantum dense coding protocols, our
scheme exploits the possibility of sending a classical message through only one
of the two entangled spatially-multimode beams, using the other one as a
reference system. We evaluate the Shannon mutual information for our protocol
and find that it is superior to the standard quantum limit. Finally, we show
how to optimize the performance of our scheme as a function of the
spatio-temporal parameters of the multimode entangled light and of the input
images.Comment: 15 pages, 4 figures, RevTeX4. Submitted to the Special Issue on
Quantum Imaging in Journal of Modern Optic
Aspects of the concept "computer literacy" in the conditions of higher professional pedagogical education
For young professionals information and communication technologies open access to knowledge, provide completely new opportunities for the acquisition of professional knowledge and creativity, and they are introduced to the values of world culture. Therefore, the formation of the information culture of the younger generation is a very important task
Feynman Diagrams and Differential Equations
We review in a pedagogical way the method of differential equations for the
evaluation of D-dimensionally regulated Feynman integrals. After dealing with
the general features of the technique, we discuss its application in the
context of one- and two-loop corrections to the photon propagator in QED, by
computing the Vacuum Polarization tensor exactly in D. Finally, we treat two
cases of less trivial differential equations, respectively associated to a
two-loop three-point, and a four-loop two-point integral. These two examples
are the playgrounds for showing more technical aspects about: Laurent expansion
of the differential equations in D (around D=4); the choice of the boundary
conditions; and the link among differential and difference equations for
Feynman integrals.Comment: invited review article from Int. J. Mod. Phys.
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