Dark matter as integration constant in Horava-Lifshitz gravity

In the non-relativistic theory of gravitation recently proposed by Horava, the Hamiltonian constraint is not a local equation satisfied at each spatial point but an equation integrated over a whole space. The global Hamiltonian constraint is less restrictive than its local version, and allows a richer set of solutions than in general relativity. We show that a component which behaves like pressureless dust emerges as an "integration constant" of dynamical equations and momentum constraint equations. Consequently, classical solutions to the infrared limit of Horava-Lifshitz gravity can mimic general relativity plus cold dark matter.Comment: 16 pages; (non-)conservation equation for "dark matter" added (v2); note added to comment on some recent preprints (v3); version accepted for publication in PRD (v4

Algorithmic approach to adiabatic quantum optimization

It is believed that the presence of anticrossings with exponentially small gaps between the lowest two energy levels of the system Hamiltonian, can render adiabatic quantum optimization inefficient. Here, we present a simple adiabatic quantum algorithm designed to eliminate exponentially small gaps caused by anticrossings between eigenstates that correspond with the local and global minima of the problem Hamiltonian. In each iteration of the algorithm, information is gathered about the local minima that are reached after passing the anticrossing non-adiabatically. This information is then used to penalize pathways to the corresponding local minima, by adjusting the initial Hamiltonian. This is repeated for multiple clusters of local minima as needed. We generate 64-qubit random instances of the maximum independent set problem, skewed to be extremely hard, with between 10^5 and 10^6 highly-degenerate local minima. Using quantum Monte Carlo simulations, it is found that the algorithm can trivially solve all the instances in ~10 iterations.Comment: 7 pages, 3 figure

Bigravity and Lorentz-violating Massive Gravity

Bigravity is a natural arena where a non-linear theory of massive gravity can be formulated. If the interaction between the metrics $f$ and $g$ is non-derivative, spherically symmetric exact solutions can be found. At large distances from the origin, these are generically Lorentz-breaking bi-flat solutions (provided that the corresponding vacuum energies are adjusted appropriately). The spectrum of linearized perturbations around such backgrounds contains a massless as well as a massive graviton, with {\em two} physical polarizations each. There are no propagating vectors or scalars, and the theory is ghost free (as happens with certain massive gravities with explicit breaking of Lorentz invariance). At the linearized level, corrections to GR are proportional to the square of the graviton mass, and so there is no vDVZ discontinuity. Surprisingly, the solution of linear theory for a static spherically symmetric source does {\em not} agree with the linearization of any of the known exact solutions. The latter coincide with the standard Schwarzschild-(A)dS solutions of General Relativity, with no corrections at all. Another interesting class of solutions is obtained where $f$ and $g$ are proportional to each other. The case of bi-de Sitter solutions is analyzed in some detail.Comment: 25 pages. v3 Typos corrected, references added. v4 Introduction extende

Spontaneous Lorentz Breaking and Massive Gravity

We study a theory where the presence of an extra spin-two field coupled to gravity gives rise to a phase with spontaneously broken Lorentz symmetry. In this phase gravity is massive, and the Weak Equivalence Principle is respected. The newtonian potentials are in general modified, but we identify an non-perturbative symmetry that protects them. The gravitational waves sector has a rich phenomenology: sources emit a combination of massless and massive gravitons that propagate with distinct velocities and also oscillate. Since their velocities differ from the speed of light, the time of flight difference between gravitons and photons from a common source could be measured.Comment: 4 page

Production, regulation and role of nitric oxide in glial cells.

In neuropathological conditions such as Alzheimer's disease, Parkinson's disease, AIDS dementia complex and multiple selerosis, activation of microglial cells and astroglial cells is evident. Under these neuropathological conditions cellular damage in the brain is considered to arise indirectly from cytotoxic substances produced by activated glial cells. One of these toxins is NO which has been demonstrated to be produced during several neuropathological conditions. High NO levels are produced by glial cells and exert neurotoxic effects. Astroglial cells and microglial cells communicate in various ways to reduce NO production by microglial cells which is essential to maintain homeostasis in the brain. The production of TGFβ by glial cells and its activation by astrocyte-derived tPA represents one mechanism by which astroglia limit NO production in the brain

The temporal sensitivity to the tactile-induced double flash illusion mediates the impact of beta oscillations on schizotypal personality traits

The coherent experience of the self and the world depends on the ability to integrate vs. segregate sensory information. Optimal temporal integration between the senses is mediated by oscillatory properties of neural activity. Previous research showed reduced temporal sensitivity to multisensory events in schizotypy, a personality trait linked to schizophrenia. Here we used the tactileinduced Double-Flash-Illusion (tDFI) to investigate the tactile-to-visual temporal sensitivity in schizotypy, as indexed by the temporal window of illusion (TWI) and its neural underpinnings. We measured EEG oscillations within the beta band, recently shown to correlate with the tDFI. We found individuals with higher schizotypal traits to have wider TWI and slower beta waves accounting for the temporal window within which they perceive the illusion. Our results indicate reduced tactile-to-visual temporal sensitivity to mediate the effect of slowed oscillatory beta activity on schizotypal personality traits. We conclude that slowed oscillatory patterns might constitute an early marker for psychosis proneness

Faster Base64 Encoding and Decoding Using AVX2 Instructions

Web developers use base64 formats to include images, fonts, sounds and other resources directly inside HTML, JavaScript, JSON and XML files. We estimate that billions of base64 messages are decoded every day. We are motivated to improve the efficiency of base64 encoding and decoding. Compared to state-of-the-art implementations, we multiply the speeds of both the encoding (~10x) and the decoding (~7x). We achieve these good results by using the single-instruction-multiple-data (SIMD) instructions available on recent Intel processors (AVX2). Our accelerated software abides by the specification and reports errors when encountering characters outside of the base64 set. It is available online as free software under a liberal license.Comment: software at https://github.com/lemire/fastbase6

Otimização dos parâmetros hidráulicos do solo por meio de modelagem inversa utilizando o programa "PEST".

As informações dos parâmetros hidráulicos de solo constituem em dados importantes em estudos com modelagem do fluxo de água, transporte de solutos ou contaminantes bem como em simulação de crescimento vegetal. O objetivo desse estudo foi otimizar os parâmetros hidráulicos do solo pelo método de modelagem inversa. Os solos pertencem a duas áreas experimentais conduzidos em área comercial de cana-de-açúcar. O programa PEST (Parameter ESTimation) foi utilizado com o intuito de minimizar a soma dos quadrados dos resíduos entre o conteúdo de água no solo medido nos dois experimentos pelo método gravimétrico, com o conteúdo de água no solo simulada pelo modelo SWAP/WOFOST. A variação do índice estatístico RMSE entre o conteúdo de água no solo medida em campo com o simulado pelo modelo foi semelhante em ambos os locais e em média apresentou valor de 0,0281 e 0,0274 m3 m-3. O método de modelagem inversa realizado pelo programa PEST mostrou ser eficaz na otimização dos parâmetros hidráulicos do solo em ambos os locais de estudo

Grid tool integration within the eMinerals Project

In this article we describe the eMinerals mini grid, which is now running in production mode. Thisis an integration of both compute and data components, the former build upon Condor, PBS and thefunctionality of Globus v2, and the latter being based on the combined use of the Storage ResourceBroker and the CCLRC data portal. We describe how we have integrated the middleware components,and the different facilities provided to the users for submitting jobs within such an environment. We willalso describe additional functionality we found it necessary to provide ourselves