Wormholes in the accelerating universe

We discuss different arguments that have been raised against the viability of the big trip process, reaching the conclusions that this process can actually occur by accretion of phantom energy onto the wormholes and that it is stable and might occur in the global context of a multiverse model. We finally argue that the big trip does not contradict any holographic bounds on entropy and information.Comment: 2 pages, LaTex, to appear in the Proceedings of the 11th Marcel Grossmann Conference, 200

Worse than a big rip?

We show that a generalised phantom Chaplygin gas can present a future singularity in a finite future cosmic time. Unlike the big rip singularity, this singularity happens for a finite scale factor, but like the big rip singularity, it would also take place at a finite future cosmic time. In addition, we define a dual of the generalised phantom Chaplygin gas which satisfies the null energy condition. Then, in a Randall-Sundrum 1 brane-world scenario, we show that the same kind of singularity at a finite scale factor arises for a brane filled with a dual of the generalised phantom Chaplygin gas.Comment: 6 pages, 4 figures, RevTeX 4. Discussion expanded and references added. Version to appear in PL

Dark Energy Accretion onto black holes in a cosmic scenario

In this paper we study the accretion of dark energy onto a black hole in the cases that dark energy is equipped with a positive cosmological constant and when the space-time is described by a Schwarzschild-de Sitter metric. It is shown that, if confronted with current observational data, the results derived when no cosmological constant is present are once again obtained in both cases.Comment: 7 pages, 3 figure

New "Bigs" in cosmology

This paper contains a detailed discussion on new cosmic solutions describing the early and late evolution of a universe that is filled with a kind of dark energy that may or may not satisfy the energy conditions. The main distinctive property of the resulting space-times is that they make to appear twice the single singular events predicted by the corresponding quintessential (phantom) models in a manner which can be made symmetric with respect to the origin of cosmic time. Thus, big bang and big rip singularity are shown to take place twice, one on the positive branch of time and the other on the negative one. We have also considered dark energy and phantom energy accretion onto black holes and wormholes in the context of these new cosmic solutions. It is seen that the space-times of these holes would then undergo swelling processes leading to big trip and big hole events taking place on distinct epochs along the evolution of the universe. In this way, the possibility is considered that the past and future be connected in a non-paradoxical manner in the universes described by means of the new symmetric solutions.Comment: 7 figures, 13 pages, RevTe

Predictability of Stratified Turbulence

In the study of geophysical fluid dynamics, predictability of dynamics at different scales still stands in the foreground of interest as one of the primary challenges. Following Lorenz's pioneering framework, several results from homogeneous and isotropic turbulence have suggested that flows with many scales of motion present limited predictability due to the inevitable contamination of error from small to large scales, even if initially confined to small scales. In this work, we investigate the predictability of freely decaying stratified turbulence, which is representative of small-scale geophysical turbulence where rotational effects are neglected. Predictability of stratified turbulence is studied using direct numerical simulations by analyzing the error growth in pairs of realizations of velocity fields departing from almost identical initial conditions. Previous studies have indicated that the finite range of predictability is determined by the slope of the flow's kinetic energy spectrum. In stratified turbulence, the shape of the energy spectrum depends on the buoyancy Reynolds number (Reb), at least when Reb is not too large. We perform a comparative analysis of spectra and perturbation upscale growth behaviour in different regimes of stratified turbulence from O(10) to unitary order of buoyancy Reynolds number. Furthermore, we explore the sensitivity of our experimental outcomes with respect to error introduction. There were no discernible changes between the behavior of the systems and their associated error dynamics while modifying the geometrical shape of the error introduction, going from a spherical domain complement to a cylindrical complement. Likewise, the experiments were insensitive to adjusting the cutoff wavenumber (kc) at which the error is introduced while keeping the same initial error kinetic energy, obtaining similar results for kc = 20,40,60,80

Host Marking Pheromone (HMP) in the Mexican Fruit Fly Anastrepha ludens

Host marking pheromones (HMPs) are used by insects to mark hosts (usually a fruit) where they have already laid eggs. The compounds serve as a deterrent to conspecifics avoiding over-infestation of hosts (i.e. repeated egg-laying into an already occupied/used host). If these HMPs are sprayed onto commercially valuable fruit they act as deterrents preventing attack by females interested in laying eggs into the valuable commodity. Having no insecticidal or toxic properties, and being natural products (or close derivatives thereof) they could be used as fruit sprays to replace insecticides, or in combination with other products to improve efficacy. This review discusses the isolation, and synthesis of the HMP of the Mexican fruit fly Anastrepha ludens a feared pest of citrus and mangos in Mexico and Central America. This compound is also recognized by females of other pestiferous species in the same genus Anastrepha distributed from the Southern USA to Northern Argentina, including many Caribbean Islands. The synthetic HMP was shown to exhibit strong electrophysiological activity against A. ludens and excellent interspecies cross recognition with other Anastrepha species. Behavioural tests confirmed the HMP deterring effect of the synthetic natural product. Further studies enabled us to drastically simplify the structure of the HMP and obtain a derivative, which we named Anastrephamide, which shows HMP deterring effects very similar to the natural product in laboratory and field tests. The potential use of such HMP derivatives in a crop protection scenario is briefly discussed

The origin of the Acheulean: the 1.7 million-year-old site of FLK West, Olduvai Gorge (Tanzania)

The appearance of the Acheulean is one of the hallmarks of human evolution. It represents the emergence of a complex behavior, expressed in the recurrent manufacture of large-sized tools, with standardized forms, implying more advance forethought and planning by hominins than those required by the precedent Oldowan technology. The earliest known evidence of this technology dates back to c. 1.7 Ma. and is limited to two sites (Kokiselei [Kenya] and Konso [Ethiopia]), both of which lack fauna. The functionality of these earliest Acheulean assemblages remains unknown. Here we present the discovery of another early Acheulean site also dating to c. 1.7 Ma from Olduvai Gorge. This site provides evidence of the earliest steps in developing the Acheulean technology and is the oldest Acheulean site in which stone tools occur spatially and functionally associated with the exploitation of fauna. Simple and elaborate large-cutting tools (LCT) and handaxes co-exist at FLK West, showing that complex cognition was present from the earliest stages of the Acheulean. Here we provide a detailed technological study and evidence of the use of these tools on the butchery and consumption of fauna, probably by early Homo erectus sensu lato