1,528 research outputs found
Channeling of high-energy particles in a multi-wall nanotube
Channeling of high-energy particles in straight and bent multi-wall nanotubes
(MWNT) has been studied in computer simulations and compared to the channeling
properties of single-wall nanotubes (SWNT) and bent crystal lattices. It is
demonstrated that MWNT can efficiently channel positively-charged high-energy
particles trapped between the walls of MWNT. Bending dechanneling in MWNT has
been computed as a function of the particle momentum to nanotube curvature
radius ratio, . It is found that a bent MWNT can steer a particle beam
with bending capabilities similar to those of bent silicon crystal lattice and
to those of best (i.e. the narrowest) SWNT. In view of channeling applications
at particle accelerators, MWNT appear favored as compared to SWNT, because MWNT
can be produced quite straight (and in aligned array), while SWNT is typically
very curved, thus posing a severe problem for channeling applications.
Therefore, we suggest that MWNT provide a better candidate for channeling than
SWNT.Comment: 16 pages, 6 figures, to appear in Phys. Lett.
GRBs with optical afterglow and known redshift: a statistical study
We present a correlation between two intrinsic parameters of GRB optical
afterglows. These are the isotropic luminosity at the maximum of the light
curve (Lpeak) and the time-integrated isotropic energy (Eiso) radiated after
the observed maximum. We test the correlation between the logarithms of (Eiso)
and (Lpeak) and finally we value the effect of the different samples of GRBs in
according with the first optical observation reduced to proper time.Comment: To be published in the proceedings of the conference "SWIFT and GRBs:
Unveiling the Relativistic Universe", Venice, June 5-9, 200
The first light of Mini-MegaTORTORA wide-field monitoring system
Here we describe the first light of the novel 9-channel wide-field optical
monitoring system with sub-second temporal resolution, Mini-MegaTORTORA, which
is being tested now at Special Astrophysical Observatory on Russian Caucasus.
The system is able to observe the sky simultaneously in either wide (~900
square degrees) or narrow (~100 square degrees) fields of view, either in clear
light or with any combination of color (Johnson B, V or R) polarimetric filters
installed, with exposure times ranging from 100 ms to 100 s. The primary goal
of the system is the detection of rapid -- with sub-second characteristic
time-scales -- optical transients, but it may be also used for studying the
variability of the sky objects on longer time scales.Comment: 9 pages, 9 figures, based on the talk presented on "Modern stellar
astronomy-2014" (Rostov-on-Don
Algebraic Insights into the Secret Feistel Network
We introduce the high-degree indicator matrix (HDIM), an object closely related with both the linear approximation table and the algebraic normal form (ANF) of a permutation. We show that the HDIM of a Feistel Network contains very specific patterns depending on the degree of the Feistel functions, the number of rounds and whether the Feistel functions are 1-to-1 or not. We exploit these patterns to distinguish Feistel Networks, even if the Feistel Network is whitened using unknown affine layers.
We also present a new type of structural attack exploiting monomials that cannot be present at round r-1 to recover the ANF of the last Feistel function of a r-round Feistel Network. Finally, we discuss the relations between our findings, integral attacks, cube attacks, Todo's division property and the congruence modulo 4 of the Linear Approximation Table
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