Sofia University

About: Sofia University is a education organization based out in Sofia, Bulgaria. It is known for research contribution in the topics: Large Hadron Collider & Standard Model. The organization has 8533 authors who have published 15730 publications receiving 306320 citations. The organization is also known as: University of Sofia & BFUS.

Stability of symmetric and unsymmetric thin liquid films to short and long wavelength perturbations

Abstract: The stability of thin (< 100 nm) symmetrical and unsymmetrical membranes, assimilated with viscous liquids, to short and long wavelength perturbations is investigated. The asymmetry is due to the two different viscous phases surrounding the membrane and to the different interfacial tensions on the two faces of the membrane. The cell membrane is a case for which the present treatment is of significance. The dynamics of the membrane to perturbations is described by the Navier-Stokes equation modified with a body force which accounts for the fact that the range of the interaction forces is larger than the thickness of the film. The body force is computed assuming pair-wise additivity and accounting for the deformation of the interface produced by the perturbation. General dispersion equations are derived, and these equations describe the squeezing and stretching modes of perturbations. The growth coefficient is expressed as a function of the wavelength for various ratios of the viscosities of the two surrounding phases and various values of the two interfacial tensions. In the limiting cases of interfacial tension ratio equal to unity and wavelength large compared to the thickness of the film results of the previous investigators are obtained. For the symmetrical case expressions are derived for the critical and dominant wavelength of the squeezing and stretching modes. An application of the results to a cell membrane shows that the growth of the instability is dominated in this case by the stretching mode since the time scale of growth of the perturbations is four orders of magnitude less than that in the squeezing mode. For unsymmetrical systems the effect of differences between the interfacial tensions on the two faces on the ratio of the amplitudes of perturbations on the two faces is investigated. The results show in what manner differences in interfacial tension convey amplified or damped messages across the membrane.

Search for additional neutral MSSM Higgs bosons in the τ τ final state in proton-proton collisions at √s=13 TeV

Abstract: A search is presented for additional neutral Higgs bosons in the τ τ final state in proton-proton collisions at the LHC. The search is performed in the context of the minimal supersymmetric extension of the standard model (MSSM), using the data collected with the CMS detector in 2016 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. To enhance the sensitivity to neutral MSSM Higgs bosons, the search includes production of the Higgs boson in association with b quarks. No significant deviation above the expected background is observed. Model-independent limits at 95% confidence level (CL) are set on the product of the branching fraction for the decay into τ leptons and the cross section for the production via gluon fusion or in association with b quarks. These limits range from 18 pb at 90 GeV to 3.5 fb at 3.2 TeV for gluon fusion and from 15 pb (at 90 GeV) to 2.5 fb (at 3.2 TeV) for production in association with b quarks, assuming a narrow width resonance. In the m h hod + scenario these limits translate into a 95% CL exclusion of tan β > 6 for neutral Higgs boson masses below 250 GeV, where tan β is the ratio of the vacuum expectation values of the neutral components of the two Higgs doublets. The 95% CL exclusion contour reaches 1.6 TeV for tan β = 60.