Exploring the liminality: properties of haloes and subhaloes in borderline f(R) gravity

We investigate the properties of dark matter haloes and subhaloes in an f(R) gravity model with |fR0| = 10−6, using a very-high-resolution N-body simulation. The model is a borderline between being cosmologically interesting and yet still consistent with current data. We find that the halo mass function in this model has a maximum 20 per cent enhancement compared with the Λ-cold-dark-matter (ΛCDM) predictions between z = 1 and 0. Because of the chameleon mechanism which screens the deviation from standard gravity in dense environments, haloes more massive than 1013 h−1 M⊙ in this f(R) model have very similar properties to haloes of similar mass in ΛCDM, while less massive haloes, such as that of the Milky Way, can have steeper inner density profiles and higher velocity dispersions due to their weaker screening. The halo concentration is remarkably enhanced for low-mass haloes in this model due to a deepening of the total gravitational potential. Contrary to the naive expectation, the halo formation time zf is later for low-mass haloes in this model, a consequence of these haloes growing faster than their counterparts in ΛCDM at late times and the definition of zf. Subhaloes, especially those less massive than 1011 h−1 M⊙, are substantially more abundant in this f(R) model for host haloes less massive than 1013 h−1 M⊙. We discuss the implications of these results for the Milky Way satellite abundance problem. Although the overall halo and subhalo properties in this borderline f(R) model are close to their ΛCDM predictions, our results suggest that studies of the Local Group and astrophysical systems, aided by high-resolution simulations, can be valuable for further tests of it

Quantum Computer with Mixed States and Four-Valued Logic

In this paper we discuss a model of quantum computer in which a state is an operator of density matrix and gates are general quantum operations, not necessarily unitary. A mixed state (operator of density matrix) of n two-level quantum systems is considered as an element of 4^n-dimensional operator Hilbert space (Liouville space). It allows to use a quantum computer model with four-valued logic. The gates of this model are general superoperators which act on n-ququat state. Ququat is a quantum state in a four-dimensional (operator) Hilbert space. Unitary two-valued logic gates and quantum operations for an n-qubit open system are considered as four-valued logic gates acting on n-ququat. We discuss properties of quantum four-valued logic gates. In the paper we study universality for quantum four-valued logic gates.Comment: 17 page

Efeito da Infestação de Larvas de Diabrotica speciosa em Tubérculos de Batata em Períodos de Calor e Frio.

bitstream/item/145138/1/Circular-171.pd

Caracterização do nível de adoção tecnológica da produção de pêssegos orgânico e convencional na região de Pelotas-RS.

bitstream/item/206986/1/Boletim-327.pd

Clues from nearby galaxies to a better theory of cosmic evolution

The great advances in the network of cosmological tests show that the relativistic Big Bang theory is a good description of our expanding universe. But the properties of nearby galaxies that can be observed in greatest detail suggest a still better theory would more rapidly gather matter into galaxies and groups of galaxies. This happens in theoretical ideas now under discussion.Comment: published in Natur

The Astropy Problem

The Astropy Project (http://astropy.org) is, in its own words, "a community effort to develop a single core package for Astronomy in Python and foster interoperability between Python astronomy packages." For five years this project has been managed, written, and operated as a grassroots, self-organized, almost entirely volunteer effort while the software is used by the majority of the astronomical community. Despite this, the project has always been and remains to this day effectively unfunded. Further, contributors receive little or no formal recognition for creating and supporting what is now critical software. This paper explores the problem in detail, outlines possible solutions to correct this, and presents a few suggestions on how to address the sustainability of general purpose astronomical software