Measurement and analysis of a small nozzle plume in vacuum

Pitot pressures and flow angles are measured in the plume of a nozzle flowing nitrogen and exhausting to a vacuum. Total pressures are measured with Pitot tubes sized for specific regions of the plume and flow angles measured with a conical probe. The measurement area for total pressure extends 480 mm (16 exit diameters) downstream of the nozzle exit plane and radially to 60 mm (1.9 exit diameters) off the plume axis. The measurement area for flow angle extends to 160 mm (5 exit diameters) downstream and radially to 60 mm. The measurements are compared to results from a numerical simulation of the flow that is based on kinetic theory and uses the direct-simulation Monte Carlo (DSMC) method. Comparisons of computed results from the DSMC method with measurements of flow angle display good agreement in the far-field of the plume and improve with increasing distance from the exit plane. Pitot pressures computed from the DSMC method are in reasonably good agreement with experimental results over the entire measurement area

Effective dynamics of the closed loop quantum cosmology

In this paper we study dynamics of the closed FRW model with holonomy corrections coming from loop quantum cosmology. We consider models with a scalar field and cosmological constant. In case of the models with cosmological constant and free scalar field, dynamics reduce to 2D system and analysis of solutions simplify. If only free scalar field is included then universe undergoes non-singular oscillations. For the model with cosmological constant, different behaviours are obtained depending on the value of $\Lambda$. If the value of $\Lambda$ is sufficiently small, bouncing solutions with asymptotic de Sitter stages are obtained. However if the value of $\Lambda$ exceeds critical value $\Lambda_{\text{c}} =\frac{\sqrt{3}m^2_{\text{Pl}}}{2\pi\gamma^3} \simeq 21 m^2_{\text{Pl}}$ then solutions become oscillatory. Subsequently we study models with a massive scalar field. We find that this model possess generic inflationary attractors. In particular field, initially situated in the bottom of the potential, is driven up during the phase of quantum bounce. This subsequently leads to the phase of inflation. Finally we find that, comparing with the flat case, effects of curvature do not change qualitatively dynamics close to the phase of bounce. Possible effects of inverse volume corrections are also briefly discussed.Comment: 18 pages, 11 figure

Heating up the cold bounce

Self-dual string cosmological models provide an effective example of bouncing solutions where a phase of accelerated contraction smoothly evolves into an epoch of decelerated Friedmann--Robertson--Walker expansion dominated by the dilaton. While the transition to the expanding regime occurs at sub-Planckian curvature scales, the Universe emerging after the bounce is cold, with sharply growing gauge coupling. However, since massless gauge bosons (as well as other massless fields) are super-adiabatically amplified, the energy density of the maximally amplified modes re-entering the horizon after the bounce can efficiently heat the Universe. As a consequence the gauge coupling reaches a constant value, which can still be perturbative.Comment: 28 pages, 13 figure

The electric dipole moment of the neutron from 2+1 flavor lattice QCD

We compute the electric dipole moment d_n of the neutron from a fully dynamical simulation of lattice QCD with 2+1 flavors of clover fermions and nonvanishing theta term. The latter is rotated into the pseudoscalar density in the fermionic action using the axial anomaly. To make the action real, the vacuum angle theta is taken to be purely imaginary. The physical value of d_n is obtained by analytic continuation. We find d_n = -3.8(2)(9) x 10^{-16} [theta e cm], which, when combined with the experimental limit on d_n, leads to the upper bound theta < 7.6 x 10^{-11}.Comment: 12 pages, 8 figures, matches PRL published versio

(B-L) Symmetry vs. Neutrino Seesaw

We compute the effective coupling of the Majoron to W bosons at \cO(\hbar) by evaluating the matrix element of the (B-L) current between the vacuum and a $W^+W^-$ state. The (B-L) anomaly vanishes, but the amplitude does not vanish as a result of a UV finite and non-local contribution which is entirely due to the mixing between left-chiral and right-chiral neutrinos. The result shows how anomaly-like couplings may arise in spite of the fact that the (B-L) current remains exactly conserved to all orders in $\hbar$, lending additional support to our previous proposal to identify the Majoron with the axion.Comment: 13 pages, 1 figure, with additional explanations and clarification

Black hole entropy in Loop Quantum Gravity

We calculate the black hole entropy in Loop Quantum Gravity as a function of the horizon area and provide the exact formula for the leading and sub-leading terms. By comparison with the Bekenstein-Hawking formula we uniquely fix the value of the 'quantum of area' in the theory.Comment: LaTeX, 10 page

Estudo de prevalência do Cassava Commom Mosaic Vírus (CsCMV) e do Cassava Vein Mosaic Virus (CsVMV) na região produtora do Estado da Bahia.

A mandioca (Manihot esculenta Crantz) é uma das principais fontes de energia na dieta humana dos países tropicais. Por ser propagada vegetativamente, através de partes caulinares (ramas ou manivas) (RODRIGUES et al., 2008), a dispersão de doenças sistêmicas, como as causadas por viroses, podem levar a degenerescência das manivas (COSTA; KITAJIMA, 1972). Em relação aos vírus de maior importância econômica no Brasil, destacam-se o mosaico das nervuras - Cassava vein mosaic virus (CsVMV), e o mosaico comum - Cassava common mosaic virus CsCMV (CHUMBINHO et al, 2010). Trabalho realizados no início da década passada consideram o mosaico das nervuras, CsVMV, como sendo um vírus de ampla abrangência geográfica, sendo prevalente, principalmente, no ecossistema do semiárido nordestino. Esse efeito não está somente associado às severas manifestações produzidas, mas também pela influência negativa na qualidade dos produtos obtidos (CHIGERU et al., 2003). Além da transmissão por material propagativo, o CsVMV é transmitido por ferramentas utilizadas para o corte das manivas. Observações de campo têm indicado que a manifestação severa da doença em variedades suscetíveis pode causar perdas de produção que variam de 10 a 20%, prejudicando a qualidade do produto, devido à redução de 10 a 50% nos teores de amido (FUKUDA, 1993). Os sintomas caracterizam-se pela presença de cloroses intensas entre as nervuras primárias e secundárias, nas plantas afetadas. Em casos severos da doença é comum observar um forte retorcimento do limbo foliar (OTSUBO et al., 2003). O CsCMV, mosaico comum, pertencente a família Flexiviridae e gênero Potexvirus (SOARES et al., 2009), não possui vetor conhecido, logo entende-se que sua disseminação ocorre mecanicamente (COLARICCIO et al., 2009). O Cassava common mosaic vírus - CsCMV é classificado como uma Potexvirus e possui uma partícula semiflexuosa de 15 nm × 495 nm (Kitajima et al., 1965). O genoma é constituído de uma fita única de RNA senso positiva (ssRNA) de 2 × 106 Da, com capsídio constituído por uma única proteína de 21 kDa de massa molecular (Nolt et al.,1991). Os sintomas apresentados em mandiocas infectadas por esse vírus são de mosaico no limbo foliar, presença de áreas cloróticas que são muitas vezes limitados pela as veias e a doença pode causar perdas de rendimento em mais de 30%. Por essa razão, alguns trabalhos apontam para a importância do cuidado que se deve ter na seleção do material de plantio, pois essas medidas podem ajudar a erradicar ou reduzir a doença a um nível econômico significativamente secundário. O objetivo do presente trabalho foi detectar, avaliar e identificar a prevalência do CsCMV e do CsVMV em diversas variedades de mandioca cultivadas nas principais regiões produtoras de mandioca do estado da Bahia

Dilaton Contributions to the Cosmic Gravitational Wave Background

We consider the cosmological amplification of a metric perturbation propagating in a higher-dimensional Brans-Dicke background, including a non trivial dilaton evolution. We discuss the properties of the spectral energy density of the produced gravitons (as well as of the associated squeezing parameter), and we show that the present observational bounds on the graviton spectrum provide significant information on the dynamical evolution of the early universe.Comment: 26 pages, plain tex (to appear in Phys.Rev.D, 1 fig available from the authors upon req.

Domain walls without cosmological constant in higher order gravity

We consider a class of higher order corrections with arbitrary power $n$ of the curvature tensor to the standard gravity action in arbitrary space-time dimension $D$. The corrections are in the form of Euler densities and are unique at each $n$ and $D$. We present a generating functional and an explicit form of the corresponding conserved energy-momentum tensors. The case of conformally flat metrics is discussed in detail. We show that this class of corrections allows for domain wall solutions since, despite the presence of higher powers of the curvature tensor, the singularity structure at the wall is of the same type as in the standard gravity. However, models with higher order corrections have larger set of domain wall solutions and the existence of these solutions no longer depends on the presence of cosmological constants. We find for example that the Randall-Sundrum scenario can be realized without any need for bulk and/or brane cosmological constant.Comment: latex, 10 pages, introduction extended, references added, typos correcte

Final state interactions in B+- to K+ K- K+- decays

Charged B decays to three charged kaons are analysed in the framework of the QCD factorization approach. The strong final state K+K-interactions are described using the kaon scalar and vector form factors. The scalar non-strange and strange form factors at low K+K- effective masses are constrained by chiral perturbation theory and satisfy the two-body unitarity conditions. The latter stem from the properties of the meson-meson amplitudes which describe all possible S-wave transitions between three coupled channels consisting of two kaons, two pions and four pions. The vector form factors are fitted to the data on the electromagnetic kaon interactions. The model results are compared with the Belle and BaBar data. Away from phi(1020) resonance, in the S-wave dominated K+K- mass spectra, a possibility for a large CP asymmetry is identified.Comment: 7 pages, 4 figures, modified version published in Physics Letters