10,095 research outputs found
Stability of Compacton Solutions of Fifth-Order Nonlinear Dispersive Equations
We consider fifth-order nonlinear dispersive type equations to
study the effect of nonlinear dispersion. Using simple scaling arguments we
show, how, instead of the conventional solitary waves like solitons, the
interaction of the nonlinear dispersion with nonlinear convection generates
compactons - the compact solitary waves free of exponential tails. This
interaction also generates many other solitary wave structures like cuspons,
peakons, tipons etc. which are otherwise unattainable with linear dispersion.
Various self similar solutions of these higher order nonlinear dispersive
equations are also obtained using similarity transformations. Further, it is
shown that, like the third-order nonlinear equations, the fifth-order
nonlinear dispersive equations also have the same four conserved quantities and
further even any arbitrary odd order nonlinear dispersive type
equations also have the same three (and most likely the four) conserved
quantities. Finally, the stability of the compacton solutions for the
fifth-order nonlinear dispersive equations are studied using linear stability
analysis. From the results of the linear stability analysis it follows that,
unlike solitons, all the allowed compacton solutions are stable, since the
stability conditions are satisfied for arbitrary values of the nonlinear
parameters.Comment: 20 pages, To Appear in J.Phys.A (2000), several modification
Phase transition between non-extremal and extremal Reissner-Nordstr\"om black holes
We discuss the phase transition between non-extremal and extremal
Reissner-Nordstr\"om black holes. This transition is considered as the
limit of the transition between the non-extremal and near-extremal
black holes.
We show that an evaporating process from non-extremal black hole to extremal
one is possible to occur, but its reverse process is not possible to occur
because of the presence of the maximum temperature.
Furthermore, it is shown that the Hawking-Page phase transition between small
and large black holes unlikely occurs in the AdS Reissner-Nordstr\"om black
holes.Comment: 12 pages, 6 figures, version to appear in MPL
Mean field baryon magnetic moments and sumrules
New developments have spurred interest in magnetic moments (-s) of
baryons. The measurement of some of the decuplet -s and the findings of
new sumrules from various methods are partly responsible for this renewed
interest. Our model, inspired by large colour approximation, is a relativistic
self consistent mean field description with a modified Richardson potential and
is used to describe the -s and masses of all baryons with up (u), down (d)
and strange (s) quarks. We have also checked the validity of the Franklin
sumrule (referred to as CGSR in the literature) and sumrules of Luty,
March-Russell and White. We found that our result for sumrules matches better
with experiment than the non-relativistic quark model prediction. We have also
seen that quark magnetic moments depend on the baryon in which they belong
while the naive quark model expects them to be constant.Comment: 7 pages, no figure, uses epl.cl
Nonmodal energy growth and optimal perturbations in compressible plane Couette flow
Nonmodal transient growth studies and estimation of optimal perturbations
have been made for the compressible plane Couette flow with three-dimensional
disturbances. The maximum amplification of perturbation energy over time,
, is found to increase with increasing Reynolds number ,
but decreases with increasing Mach number . More specifically, the optimal
energy amplification (the supremum of over both the
streamwise and spanwise wavenumbers) is maximum in the incompressible limit and
decreases monotonically as increases. The corresponding optimal streamwise
wavenumber, , is non-zero at M=0, increases with increasing
, reaching a maximum for some value of and then decreases, eventually
becoming zero at high Mach numbers. While the pure streamwise vortices are the
optimal patterns at high Mach numbers, the modulated streamwise vortices are
the optimal patterns for low-to-moderate values of the Mach number. Unlike in
incompressible shear flows, the streamwise-independent modes in the present
flow do not follow the scaling law , the reasons
for which are shown to be tied to the dominance of some terms in the linear
stability operator. Based on a detailed nonmodal energy analysis, we show that
the transient energy growth occurs due to the transfer of energy from the mean
flow to perturbations via an inviscid {\it algebraic} instability. The decrease
of transient growth with increasing Mach number is also shown to be tied to the
decrease in the energy transferred from the mean flow () in
the same limit
A comparison of ultraviolet sensitivities in universal, nonuniversal, and split extra dimensional models
We discuss the origin of ultraviolet sensitivity in extra dimensional
theories, and compare and contrast the cutoff dependences in universal,
nonuniversal and split five dimensional models. While the gauge bosons and
scalars are in the five dimensional bulk in all scenarios, the locations of the
fermions are different in different cases. In the universal model all fermions
can travel in the bulk, in the nonuniversal case they are all confined at the
brane, while in the split scenario some are in the bulk and some are in the
brane. A possible cure from such divergences is also discussed.Comment: 9 pages, Latex, no figure, v2: further clarifications and references
added, accepted for publication in Phys. Rev.
Intrinsic noise induced resonance in presence of sub-threshold signal in Brusselator
In a system of non-linear chemical reactions called the Brusselator, we show
that {\it intrinsic noise} can be regulated to drive it to exhibit resonance in
the presence of a sub-threshold signal. The phenomena of periodic stochastic
resonance and aperiodic stochastic resonance, hitherto studied mostly with
extrinsic noise, is demonstrated here to occur with inherent systemic noise
using exact stochastic simulation algorithm due to Gillespie. The role of
intrinsic noise in a couple of other phenomena is also discussed.Comment: 7 pages, 5 figure
Spin liquid behaviour in Jeff=1/2 triangular lattice Ba3IrTi2O9
Ba3IrTi2O9 crystallizes in a hexagonal structure consisting of a layered
triangular arrangement of Ir4+ (Jeff=1/2). Magnetic susceptibility and heat
capacity data show no magnetic ordering down to 0.35K inspite of a strong
magnetic coupling as evidenced by a large Curie-Weiss temperature=-130K. The
magnetic heat capacity follows a power law at low temperature. Our measurements
suggest that Ba3IrTi2O9 is a 5d, Ir-based (Jeff=1/2), quantum spin liquid on a
2D triangular lattice.Comment: 10 pages including supplemental material, to be published in Phys.
Rev. B (Rapid Comm.
A STUDY OF POWER LINE INTERFERENCE CANCELLATION USING IIR, AAPTIVE AND WAVELET FILTERING IN ECG
Background: It is essential to reduce these disturbances in ECG signal to improve accuracy and reliability. The bandwidth of the noise overlaps that of wanted signals, so that simple filtering cannot sufficiently enhance the signal to noise ratio. The present paper deals with the digital filtering method to reduce 50 Hz power line noise artifacts in the ECG signal. 4th order Butterworth notch filters(BW=.5 Hz) is used to reduce 50 Hz power line noise interference(PLI) from ECG signals and its performance is compared with Adaptve filters. Method: ECG signal is taken from physionet database. ECG signal (with PLI noise of different frequencies) were processed by Butterworth notch filters of bandwidths of 0.5 Hz. Ringing Artifact is observed in the output. ECG signal (with PLI noise of different frequencies) were processed by Adaptive filters no ringing effect seen. Wavelet filtering applied clean ECG were observed. Result: Performance is compared based on SNR and MSE of Butterworth notch filter and adaptive filters and output of wallet filtering were observed. Conclusion: RLS adaptive filter give better performance as compared to IIR Butterworth and LMS. Clean ECG were seen when filtering using symlet8 wavelet was done
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