816 research outputs found
Ghosts and Tachyons in the Fifth Dimension
We present several solutions for the five dimensional gravity models in the
presence of bulk ghosts and tachyons to argue that these "troublesome" fields
can be a useful model-building tool. The ghost-like signature of the kinetic
term for a bulk scalar creates a minimum in the scale factor, removing the
necessity for a negative tension brane in models with the compactified fifth
dimension. It is shown that the model with the positive tension branes and a
ghost field in the bulk leads to the radion stabilization. The bulk scalar with
the variable sign kinetic term can be used to model both positive and negative
tension branes of a finite width in the compact dimension. Finally, we present
several ghost and tachyon field configurations in the bulk that lead to the
localization of gravity in four dimensions, including one solution with the
Gaussian profile for the metric, g_{\mu\nu}(y)=\eta_{\mu\nu}\exp{-\alpha y^2},
which leads to a stronger localization of gravity than the Randall-Sundrum
model.Comment: New references adde
Direct and trans-generational effects of male and female gut microbiota in Drosophila melanogaster
Funding This study was supported by the National Council for Scientific and Technological Development (CNPq). Acknowledgement We acknowledge Stuart Wigby, Adam Wong and Phil Taylor for discussion and support during the experiment.Peer reviewedPublisher PD
Aeroacoustic data for high Reynolds number supersonic axisymmetric jets
Both aerodynamic and near field acoustic behavior of several unheated axisymmetric shock free and shock containing high speed jet plumes are reported. The exit Mach number range for these data is from 0.9 to 2.5. The aerodynamic measurements include both mean and turbulence quantities for a shock free jet plume produced by a convergent divergent nozzle designed to have an exit Mach number of 2. The near field acoustic measurements presented include narrow band spectra, directivity and contour plots of select one third octave band data, and near field microphone correlations from a linear array. Shock noise results are also included as obtained by operating an underexpanded convergent nozzle at the design point of two supersonic exist Mach number convergent divergent nozzles
Reinventing PowerPoint: A New Look at an Old Tool
Microsoft PowerPoint is a powerful, yet often underutilized, orchestration tool for learning. While its most common use may be no more powerful or effective than an overhead projector, the multimedia capabilities of the software open up powerful means to connect with diverse learners in the classroom. In this piece, we explore how PowerPoint can be used in ways that connect with Universal Design for Learning principles and make teacher and student presentations more engaging and effective. We offer several concrete examples of âthinking outside the slideâ to leverage the unique potential of PowerPoint in the classroom
Spacetime structure of the global vortex
We analyse the spacetime structure of the global vortex and its maximal
analytic extension in an arbitrary number of spacetime dimensions. We find that
the vortex compactifies space on the scale of the Hubble expansion of its
worldvolume, in a manner reminiscent of that of the domain wall. We calculate
the effective volume of this compactification and remark on its relevance to
hierarchy resolution with extra dimensions. We also consider strongly
gravitating vortices and derive bounds on the existence of a global vortex
solution.Comment: 19 pages revtex, 2 figures, minor changes, references adde
Supersymmetry and Electroweak Breaking in the Interval
Hypermultiplets are considered in the five-dimensional interval where all
fields are continuous and the boundary conditions are dynamically obtained from
the action principle. The orbifold boundary conditions are obtained as
particular cases. We can interpret the Scherk-Schwarz supersymmetry breaking as
a misalignment of boundary conditions while a new source of supersymmetry
breaking corresponding to a mismatch of different boundary parameters is
identified. The latter can be viewed as coming from boundary supersymmetry
breaking masses for hyperscalars and the nature of the corresponding
supersymmetry breaking parameter is analyzed. For some regions of the parameter
space where supersymmetry is broken (either by Scherk-Schwarz boundary
conditions or by boundary hyperscalar masses) electroweak symmetry breaking can
be triggered at the tree level.Comment: 28 pages, 5 figure
Material-independent crack arrest statistics: Application to indentation experiments
An extensive experimental study of indentation and crack arrest statistics is
presented for four different brittle materials (alumina, silicon carbide,
silicon nitride, glass). Evidence is given that the crack length statistics can
be described by a universal (i.e. material independent) distribution. The
latter directly derives from results obtained when modeling crack propagation
as a depinning phenomenon. Crack arrest (or effective toughness) statistics
appears to be fully characterized by two parameters, namely, an asymptotic
crack length (or macroscopic toughness) value and a power law size dependent
width. The experimental knowledge of the crack arrest statistics at one given
scale thus gives access to its knowledge at all scales
Leaf wax biomarkers in transit record river catchment composition
Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 41 (2014): 6420â6427, doi:10.1002/2014GL061328.Rivers carry organic molecules derived from terrestrial vegetation to sedimentary deposits in lakes and oceans, storing information about past climate and erosion, as well as representing a component of the carbon cycle. It is anticipated that sourcing of organic matter may not be uniform across catchments with substantial environmental variability in topography, vegetation zones, and climate. Here we analyze plant leaf wax biomarkers in transit in the Madre de Dios River (Peru), which drains a forested catchment across 4.5âkm of elevation from the tropical montane forests of the Andes down into the rainforests of Amazonia. We find that the hydrogen isotopic composition of leaf wax molecules (specifically the C28 n-alkanoic acid) carried by this tropical mountain river largely records the elevation gradient defined by the isotopic composition of precipitation, and this supports the general interpretation of these biomarkers as proxy recorders of catchment conditions. However, we also find that leaf wax isotopic composition varies with river flow regime over storm and seasonal timescales, which could in some cases be quantitatively significant relative to changes in the isotopic composition of precipitation in the past. Our results inform on the sourcing and transport of material by a major tributary of the Amazon River and contribute to the spatial interpretation of sedimentary records of past climate using the leaf wax proxy.This work was supported by funding from the U.S. National Science Foundation award 1227192 to A.J.W. and S.J.F. V.G. was supported by the U.S. National Science Foundation award OCE-0928582.2015-03-2
New Form of the T-Duality Due to the Stability of a Compact Dimension
We study behaviors of a compact dimension and the -duality, in the
presence of the wrapped closed bosonic strings. When the closed strings
interact and form another system of strings, the radius of compactification
increases. This modifies the -duality, which we call it as -duality-like.
Some effects of the -duality-like will be studied.Comment: 12 pages, Latex, no figur
Extraordinary Phenomenology from Warped Flavor Triviality
Anarchic warped extra dimensional models provide a solution to the hierarchy
problem. They can also account for the observed flavor hierarchies, but only at
the expense of little hierarchy and CP problems, which naturally require a
Kaluza-Klein (KK) scale beyond the LHC reach. We have recently shown that when
flavor issues are decoupled, and assumed to be solved by UV physics, the
framework's parameter space greatly opens. Given the possibility of a lower KK
scale and composite light quarks, this class of flavor triviality models enjoys
a rather exceptional phenomenology, which is the focus of this letter. We also
revisit the anarchic RS EDM problem, which requires m_{KK} > 8 TeV, and show
that it is solved within flavor triviality models. Interestingly, our framework
can induce a sizable differential t \bar{t} forward-backward asymmetry, and
leads to an excess of massive boosted di-jet events, which may be linked to the
recent findings of the CDF collaboration. This feature may be observed by
looking at the corresponding planar flow distribution, which is presented here.
Finally we point out that the celebrated standard model preference towards a
light Higgs is significantly reduced within our framework.Comment: 6 pages, 3 figures. Updated the EDM bound on the anarchic scenario;
extended discussion on the KK gluon's width, discovery potential and
resulting dijet signal; matches published versio
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