10,653 research outputs found
On the origin of the Korteweg-de Vries equation
The Korteweg-de Vries equation has a central place in a model for waves on
shallow water and it is an example of the propagation of weakly dispersive and
weakly nonlinear waves. Its history spans a period of about sixty years,
starting with experiments of Scott Russell in 1834, followed by theoretical
investigations of, among others, Lord Rayleigh and Boussinesq in 1871 and,
finally, Korteweg and De Vries in 1895.
In this essay we compare the work of Boussinesq and Korteweg-de Vries,
stressing essential differences and some interesting connections. Although
there exist a number of articles, reviewing the origin and birth of the
Korteweg-de Vries equations, connections and differences, not generally known,
are reported.Comment: minor corrections; 25 pages, 3 figure
Probing the Nature of the Vela X Cocoon
Vela X is a pulsar wind nebula (PWN) associated with the active pulsar
B0833-45 and contained within the Vela supernova remnant (SNR). A collimated
X-ray filament ("cocoon") extends south-southwest from the pulsar to the center
of Vela X. VLA observations uncovered radio emission coincident with the
eastern edge of the cocoon and H.E.S.S. has detected TeV -ray emission
from this region as well. Using XMM-\textit{Newton} archival data, covering the
southern portion of this feature, we analyze the X-ray properties of the
cocoon. The X-ray data are best fit by an absorbed nonequilibrium plasma model
with a powerlaw component. Our analysis of the thermal emission shows enhanced
abundances of O, Ne, and Mg within the cocoon, indicating the presence of
ejecta-rich material from the propagation of the SNR reverse shock, consistent
with Vela X being a disrupted PWN. We investigate the physical processes that
excite the electrons in the PWN to emit in the radio, X-ray and -ray
bands. The radio and non-thermal X-ray emission can be explained by synchrotron
emission. We model the -ray emission by Inverse Compton scattering of
electrons off of cosmic microwave background (CMB) photons. We use a
3-component broken power law to model the synchrotron emission, finding an
intrinsic break in the electron spectrum at keV and a
cooling break at 5.5 keV. This cooling break along with
a magnetic field strength of 5 G indicate that the synchrotron
break occurs at 1 keV.Comment: accepted for publication to ApJ
Physics Opportunities for Vector-Boson Scattering at a Future 100 TeV Hadron Collider
Vector-boson scattering (VBS) processes provide particularly promising means
for probing the mechanism of electroweak symmetry breaking and to search for
new physics in the weak sector. In the environment of a future proton-proton
collider operating at a center-of-mass energy of 100 TeV, unprecedented
opportunities arise for the investigation of this important class of reactions.
We highlight the prominent features of VBS processes in this energy regime and
discuss how the VBS signal can be isolated in the presence of a priori large
QCD backgrounds. We find excellent opportunities for the analysis of VBS
reactions in a kinematic range that is inaccessible to present colliders.Comment: 26 pages, 14 figures; matches version published by Phys. Rev.
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Security analysis of the micro transport protocol with a misbehaving receiver
BitTorrent is the most widely used Peer-to-Peer (P2P) protocol and it comprises the largest share of traffic in Europe. To make BitTorrent more Internet Service Provider (ISP) friendly, BitTorrent Inc. invented the Micro Transport Protocol (uTP). It is based on UDP with a novel congestion control called Low Extra Delay Background Transport (LEDBAT). This protocol assumes that the receiver always gives correct feedback, since otherwise this deteriorates throughput or yields to corrupted data. We show through experimental investigation that a misbehaving uTP receiver, which is not interested in data integrity, can increase the bandwidth of the sender by up to five times. This can cause a congestion collapse and steal large share of a victim’s bandwidth. We present three attacks, which increase the bandwidth usage significantly. We have tested these attacks in a real world environment and show its severity both in terms of number of packets and total traffic generated. We also present a countermeasure for protecting against the attacks and evaluate the performance of that defence strategy
Universal Unitarity Triangle and Physics Beyond the Standard Model
We make the simple observation that there exists a universal unitarity
triangle for all models, like the SM, the Two Higgs Doublet Models I and II and
the MSSM with minimal flavour violation, that do not have any new operators
beyond those present in the SM and in which all flavour changing transitions
are governed by the CKM matrix with no new phases beyond the CKM phase. This
universal triangle can be determined in the near future from the ratio (Delta
M)_d/(Delta M)_s and sin(2 beta) measured first through the CP asymmetry in
B_d^0 to psi K_S and later in K to pi nu nubar decays. Also suitable ratios of
the branching ratios for B to X_{d,s} nu nubar and B_{d,s} to mu^+ mu^- and the
angle gamma measured by means of CP asymmetries in B decays can be used for
this determination. Comparison of this universal triangle with the
non-universal triangles extracted in each model using epsilon, (Delta M)_d and
various branching ratios for rare decays will allow to find out in a
transparent manner which of these models, if any, is singled out by experiment.
A virtue of the universal triangle is that it allows to separate the
determination of the CKM parameters from the determination of new parameters
present in the extensions of the SM considered here.Comment: 12 pages, 1 figur
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Destabilizing BitTorrent's clusters to attack high bandwidth lechers
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