Keck Deep Fields. III. Luminosity-dependent Evolution of the Ultraviolet Luminosity and Star Formation Rate Densities at z~4, 3, and 2

We use the Keck Deep Fields UGRI catalog of z~4, 3, and 2 UV-selected galaxies to study the evolution of the rest-frame 1700A luminosity density at high redshift. The ability to reliably constrain the contribution of faint galaxies is critical and our data do so as they reach to M*+2 even at z~4 and deeper still at lower redshifts. We find that the luminosity density at high redshift is dominated by the hitherto poorly studied galaxies fainter than L*, and, indeed, the the bulk of the UV light in the high-z Universe comes from galaxies in the luminosity range L=0.1-1L*. It is these faint galaxies that govern the behavior of the total UV luminosity density. Overall, there is a gradual rise in luminosity density starting at z~4 or earlier, followed by a shallow peak or a plateau within z~3--1, and then followed by the well-know plunge at lower redshifts. Within this total picture, luminosity density in sub-L* galaxies evolves more rapidly at high redshift, z>~2, than that in more luminous objects. However, this is reversed at lower redshifts, z<~1, a reversal that is reminiscent of galaxy downsizing. Within the context of the models commonly used in the observational literature, there seemingly aren't enough faint or bright LBGs to maintain ionization of intergalactic gas even as late as z~4. This is particularly true at earlier epochs and even more so if the faint-end evolutionary trends we observe at z~3 and 4 continue to higher redshifts. Apparently the Universe must be easier to reionize than some recent studies have assumed. Nevertheless, sub-L* galaxies do dominate the total UV luminosity density at z>~2 and this dominance further highlights the need for follow-up studies that will teach us more about these very numerous but thus far largely unexplored systems.Comment: Accepted for publication in the Astrophysical Journal. Abstract abridge

Social Networks through the Prism of Cognition

Human relations are driven by social events - people interact, exchange information, share knowledge and emotions, or gather news from mass media. These events leave traces in human memory. The initial strength of a trace depends on cognitive factors such as emotions or attention span. Each trace continuously weakens over time unless another related event activity strengthens it. Here, we introduce a novel Cognition-driven Social Network (CogSNet) model that accounts for cognitive aspects of social perception and explicitly represents human memory dynamics. For validation, we apply our model to NetSense data on social interactions among university students. The results show that CogSNet significantly improves quality of modeling of human interactions in social networks

Geobotanical and sozological valorization of natural habitats in selected areas of the Blue-Green Network

One of the key components of The Blue-Green Network in Łódź are valuable natural areas like the relicts of the natural wildlife (called “Green Treasures of Łódź”) which parts have been preserved in Łódź in spite of two hundred years, very intense urbanization processes. The result of years of geobotanical research in the city was establishing 23 areas of nature protection and proposing of 12 additional natural areas which need to be protected (8 areas of landscape protection and 4 ecological sites). Existing and proposed areas of nature protection, including river valleys, build the wildlife system of Łódź. Predominantly the important role in this concept play the Łódź’s river valleys with their vegetation potential. The Sokolowka River Valley which is located in the Northern-West part of Łódź was the exemplary research field for geobotanical and sozological valorization of the natural habitat of the Blue-Green Network. Within the Sokolowka valley there are retained fragments of precious nature ecosystems.Zadanie pt. „Digitalizacja i udostępnienie w Cyfrowym Repozytorium Uniwersytetu Łódzkiego kolekcji czasopism naukowych wydawanych przez Uniwersytet Łódzki” nr 885/P-DUN/2014 dofinansowane zostało ze środków MNiSW w ramach działalności upowszechniającej naukę

Inert-states of spin-5 and spin-6 Bose-Einstein condensates

In this paper we consider spinor Bose-Einstein condensates with spin f=5 and f=6 in the presence and absence of external magnetic field at the mean field level. We calculate all of so-called inert-states of these systems. Inert-states are very unique class of stationary states because they remain stationary while Hamiltonian parameters change. Their existence comes from Michel's theorem. For illustration of symmetry properties of the inert-states we use method that allows classification of the systems as a polyhedron with 2f vertices proposed by R. Barnett et al., Phys. Rev. Lett. 97, 180412 (2006).Comment: 19 pages, 4 figure

Unifying parameter estimation and the Deutsch-Jozsa algorithm for continuous variables

We reveal a close relationship between quantum metrology and the Deutsch-Jozsa algorithm on continuous-variable quantum systems. We develop a general procedure, characterized by two parameters, that unifies parameter estimation and the Deutsch-Jozsa algorithm. Depending on which parameter we keep constant, the procedure implements either the parameter-estimation protocol or the Deutsch-Jozsa algorithm. The parameter-estimation part of the procedure attains the Heisenberg limit and is therefore optimal. Due to the use of approximate normalizable continuous-variable eigenstates, the Deutsch-Jozsa algorithm is probabilistic. The procedure estimates a value of an unknown parameter and solves the Deutsch-Jozsa problem without the use of any entanglement