University of Warsaw

About: University of Warsaw is a education organization based out in Warsaw, Poland. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 20832 authors who have published 56617 publications receiving 1185084 citations. The organization is also known as: Uniwersytet Warszawski & Warsaw University.

Predation and the evolution of vertical migration in zooplankton

Abstract: Diel vertical migrations of zooplankton within water bodies have been related to efficient utilization of resources1–4 or to avoidance of mortality due to predation5,6. Although the possibility that vertical migrations evolved as an antipredator strategy has attracted much attention, no evidence has yet been presented of predation selecting for traits of migratory behaviour in planktonic animals. Therefore, I have examined nonmigratory and migratory populations of a copepod, Cyclops abyssorum, in alpine clear-water lakes in the Tatra Mountains of Poland. I report here that diel vertical migrations are not apparent in lakes without predatory fish, whereas short-range migrations are demonstrable in lakes which have been stocked with planktivorous fishes for decades, and long-range migrations are evident in lakes that have been stocked for centuries or millennia. These observations support the view that migratory behaviour in zooplankton is selected for as a means of evading fish predators.

Search for neutral MSSM Higgs bosons at LEP

Abstract: The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric standard model (MSSM). The data of the four collaborations are statistically combined and examined for their consistency with the background hypothesis and with a possible Higgs boson signal. The combined LEP data show no significant excess of events which would indicate the production of Higgs bosons. The search results are used to set upper bounds on the cross-sections of various Higgs-like event topologies. The results are interpreted within the MSSM in a number of “benchmark” models, including CP-conserving and CP-violating scenarios. These interpretations lead in all cases to large exclusions in the MSSM parameter space. Absolute limits are set on the parameter cosβ and, in some scenarios, on the masses of neutral Higgs bosons.

The dawn of FIMP Dark Matter : A review of models and constraints

Abstract: We present an overview of scenarios where the observed Dark Matter (DM) abundance consists of Feebly Interacting Massive Particles (FIMPs), produced nonthermally by the so-called freeze-in mechanism. In contrast to the usual freeze-out scenario, frozen-in FIMP DM interacts very weakly with the particles in the visible sector and never attained thermal equilibrium with the baryon–photon fluid in the early Universe. Instead of being determined by its annihilation strength, the DM abundance depends on the decay and annihilation strengths of particles in equilibrium with the baryon–photon fluid, as well as couplings in the DM sector. This makes frozen-in DM very difficult but not impossible to test. In this review, we present the freeze-in mechanism and its variations considered in the literature (dark freeze-out and reannihilation), compare them to the standard DM freeze-out scenario, discuss several aspects of model building, and pay particular attention to observational properties and general testability o...