Clustering of Primordial Black Holes. II. Evolution of Bound Systems

Primordial Black Holes (PBHs) that form from the collapse of density perturbations are more clustered than the underlying density field. In a previous paper, we showed the constraints that this has on the prospects of PBH dark matter. In this paper we examine another consequence of this clustering: the formation of bound systems of PBHs in the early universe. These would hypothetically be the earliest gravitationally collapsed structures, forming when the universe is still radiation dominated. Depending upon the size and occupation of the clusters, PBH merging occurs before they would have otherwise evaporated due to Hawking evaporation.Comment: 23 pages, 1 figure. Submitted to PR

Lugar, região, nação, mundo: explorações históricas do debate acerca das escalas da ação política

A partir de uma revisão teórica da noção de escala e de uma recuperação do debate socialista no século XIX a respeito de nacionalismo e internacionalismo, o artigo pretende lançar um novo olhar sobre a discussão contemporânea acerca da escala pertinente da ação política e do planejamento. Rejeitando a possibilidade de que qualquer estratégia efetivamente transformadora se inscreva numa única e privilegiada escala – local, regional, nacional ou global –, a conclusão sugere que o poder, mais do que nunca, não está nem no local nem no regional, nem no nacional nem no global… mas na capacidade de articular escalas, de analisar e intervir de modo transescalar.

Planejamento territorial e projeto nacional: os desafios da fragmentação

A história recente do planejamento territorial no Brasil poderia ser narrada como uma trajetória continuada, embora não linear, de desconstituição – política, intelectual e institucional. Este processo é resultado e fator de aceleração do processo de fragmentação territorial que desafia todos os que se preocupam com a necessidade de um projeto nacional digno desta abrangência. O presente trabalho busca identificar e analisar os principais vetores do processo de fragmentação, a saber: grandes projetos de investimento (GPIs), neo-localismo competitivo e o velho regionalismo, com suas redes de clientela-patronagem. Em seguida, são examinados rapidamente os referentes teórico-conceituais dos GPIs e, em particular, do neo-localismo competitivo, que constitui hoje a principal receita distribuída aos países periféricos e dependentes por agências multilaterais e consultores internacionais. Ao final, busca-se explorar em que medida estariam emergindo no processo social contemporâneo tendências e forças capazes de neutralizarem os vetores da fragmentação e conduzirem um projeto nacional, no qual, necessariamente, o planejamento territorial deverá ocupar lugar central.

Astrophysical constraints on primordial black holes in Brans-Dicke theory

We consider cosmological evolution in Brans-Dicke theory with a population of primordial black holes. Hawking radiation from the primordial black holes impacts various astrophysical processes during the evolution of the Universe. The accretion of radiation by the black holes in the radiation dominated era may be effective in imparting them a longer lifetime. We present a detailed study of how this affects various standard astrophysical constraints coming from the evaporation of primordial black holes. We analyze constraints from the present density of the Universe, the present photon spectrum, the distortion of the cosmic microwave background spectrum and also from processes affecting light element abundances after nucleosynthesis. We find that the constraints on the initial primordial black hole mass fractions are tightened with increased accretion efficiency.Comment: 15 page

Generalised constraints on the curvature perturbation from primordial black holes

Primordial black holes (PBHs) can form in the early Universe via the collapse of large density perturbations. There are tight constraints on the abundance of PBHs formed due to their gravitational effects and the consequences of their evaporation. These abundance constraints can be used to constrain the primordial power spectrum, and hence models of inflation, on scales far smaller than those probed by cosmological observations. We compile, and where relevant update, the constraints on the abundance of PBHs before calculating the constraints on the curvature perturbation, taking into account the growth of density perturbations prior to horizon entry. We consider two simple parameterizations of the curvature perturbation spectrum on the scale of interest: constant and power-law. The constraints from PBHs on the amplitude of the power spectrum are typically in the range 10^{-2}-10^{-1} with some scale dependence.Comment: 10 pages, 2 figures, version to appear in Phys. Rev. D with minor change to calculation of constraints for spectral index not equal to on

Blue spectra and induced formation of primordial black holes

We investigate the statistical properties of primordial black hole (PBH) formation in the very early Universe. We show that the high level of inhomogeneity of the early Universe leads to the formation of the first generation PBHs. %The existence of these PBHs This causes later the appearance of a dust-like phase of the cosmological expansion. We discuss here a new mechanism for the second generation of PBH formation during the dust-like phase. This mechanism is based on the coagulation process. We demonstrate that the blue power spectrum of initial adiabatic perturbations after inflation leads to overproduction of primordial black holes with $10^9$g$\le M\le10^{15}$g if the power index is $n\ge1.2$.Comment: 16 pages, 2 figure

Cosmological constraints on primordial black holes produced in the near-critical gravitational collapse

The mass function of primordial black holes created through the near-critical gravitational collapse is calculated in a manner fairly independent of the statistical distribution of underlying density fluctuation, assuming that it has a sharp peak on a specific scale. Comparing it with various cosmological constraints on their mass spectrum, some newly excluded range is found in the volume fraction of the region collapsing into black holes as a function of the horizon mass.Comment: 9 pages. Typos corrected. To appear in Physical Review

Primordial black hole constraints in cosmologies with early matter domination

Moduli fields, a natural prediction of any supergravity and superstring-inspired supersymmetry theory, may lead to a prolonged period of matter domination in the early Universe. This can be observationally viable provided the moduli decay early enough to avoid harming nucleosynthesis. If primordial black holes form, they would be expected to do so before or during this matter dominated era. We examine the extent to which the standard primordial black hole constraints are weakened in such a cosmology. Permitted mass fractions of black holes at formation are of order $10^{-8}$, rather than the usual $10^{-20}$ or so. If the black holes form from density perturbations with a power-law spectrum, its spectral index is limited to $n \lesssim 1.3$, rather than the $n \lesssim 1.25$ obtained in the standard cosmology.Comment: 7 pages RevTeX file with four figures incorporated (uses RevTeX and epsf). Also available by e-mailing ARL, or by WWW at http://star-www.maps.susx.ac.uk/papers/infcos_papers.htm