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 $\alpha$-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 $\sim -10$ at $\sqrt{s}=1.5$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