2,417 research outputs found
The hydraulic bump: The surface signature of a plunging jet
When a falling jet of fluid strikes a horizontal fluid layer, a hydraulic
jump arises downstream of the point of impact provided a critical flow rate is
exceeded. We here examine a phenomenon that arises below this jump threshold, a
circular deflection of relatively small amplitude on the free surface, that we
call the hydraulic bump. The form of the circular bump can be simply understood
in terms of the underlying vortex structure and its height simply deduced with
Bernoulli arguments. As the incoming flux increases, a breaking of axial
symmetry leads to polygonal hydraulic bumps. The relation between this
polygonal instability and that arising in the hydraulic jump is discussed. The
coexistence of hydraulic jumps and bumps can give rise to striking nested
structures with polygonal jumps bound within polygonal bumps. The absence of a
pronounced surface signature on the hydraulic bump indicates the dominant
influence of the subsurface vorticity on its instability
Electroweak corrections to Higgs production through ZZ fusion at the linear collider
We present the full order alpha electroweak radiative corrections to e+e- ->
e+e-H. The computation is performed with the help of GRACE-loop. The extraction
of the full QED corrections is performed, these are quite large at threshold.
The genuine weak corrections, for the linear collider energies, when expressed
in the G_mu scheme are of order -2 to -4 for Higgs masses preferred by the
latest precision data. We also extract the m_t^2 type corrections and make a
comparison with the weak corrections for the process e+e- ->nu nu H.Comment: 16 pages and 6 figure
Comparison of SUSY spectrum calculations and impact on the relic density constraints from WMAP
We compare results of four public supersymmetric (SUSY) spectrum codes,
Isajet, Softsusy, Spheno and Suspect to estimate the present-day uncertainty in
the calculation of the relic density of dark matter in mSUGRA models. We find
that even for mass differences of about 1% the spread in the obtained relic
densities can be 10%. In difficult regions of the parameter space, such as
large tan(beta) or large m_0, discrepancies in the relic density are much
larger. We also find important differences in the stau co-annihilation region.
We show the impact of these uncertainties on the bounds from WMAP for several
scenarios, concentrating on the regions of parameter space most relevant for
collider phenomenology. We also discuss the case of non-zero A_0 and the stop
co-annihilation region. Moreover, we present a web application for the online
comparison of the spectrum codes.Comment: 26 pages, 6 figures, 10 tables; version to appear in PR
Full order alpha electroweak corrections to double Higgs-strahlung at the linear collider
We present the full order alpha electroweak radiative corrections to the
double Higgs-strahlung process e+e- --> ZHH. The computation is performed with
the help of GRACE-loop. After subtraction of the initial state QED radiative
corrections, we find that the genuine weak corrections in the -scheme
are small for Higgs masses and energies where this cross section is largest and
is most likely to be studied. These corrections decrease with increasing
energies attaining about at TeV. The full order alpha
correction on the other hand is quite large at threshold but small at energies
around the peak. We also study changes in the shape of the invariant mass of
the Higgs pair which has been shown to be a good discriminating variable for
the measurement of the triple Higgs vertex in this reaction.Comment: 18 pages, 5 figures and 3 table
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