Partial Transmutation of Singularities in Optical Instruments

Some interesting optical instruments such as the Eaton lens and the Invisible Sphere require singularities of the refractive index for their implementation. We show how to transmute those singularities into harmless topological defects in anisotropic media without the need for anomalous material properties

Dynamically tunable transformation thermodynamics

Recently, the introduction of transformation thermodynamics has provided a way to design thermal media that alter the flow of heat according to any spatial deformation, enabling the construction of novel devices such as thermal cloaks or concentrators. However, in its current version, this technique only allows static deformations of space. Here, we develop a space-time theory of transformation thermodynamics that incorporates the possibility of performing time-varying deformations. This extra freedom greatly widens the range of achievable effects, providing an additional degree of control for heat management applications. As an example, we design a reconfigurable thermal cloak that can be opened and closed dynamically, therefore being able to gradually adjust the temperature distribution of a given region.C G-M acknowledges support from Generalitat Valenciana through the VALi+d postdoctoral program (exp APOSTD/2014/044).García Meca, C.; Barceló, C. (2016). Dynamically tunable transformation thermodynamics. Journal of Optics. 18(4):044026-1-044026-5. https://doi.org/10.1088/2040-8978/18/4/044026S044026-1044026-5184Guenneau, S., Amra, C., & Veynante, D. (2012). Transformation thermodynamics: cloaking and concentrating heat flux. Optics Express, 20(7), 8207. doi:10.1364/oe.20.008207Schittny, R., Kadic, M., Guenneau, S., & Wegener, M. (2013). Experiments on Transformation Thermodynamics: Molding the Flow of Heat. Physical Review Letters, 110(19). doi:10.1103/physrevlett.110.195901McCall, M. W., Favaro, A., Kinsler, P., & Boardman, A. (2011). A spacetime cloak, or a history editor. Journal of Optics, 13(2), 029501-029501. doi:10.1088/2040-8978/13/2/029501Cummer, S. A., & Thompson, R. T. (2010). Frequency conversion by exploiting time in transformation optics. Journal of Optics, 13(2), 024007. doi:10.1088/2040-8978/13/2/024007García-Meca, C., Carloni, S., Barceló, C., Jannes, G., Sánchez-Dehesa, J., & Martínez, A. (2013). Analogue Transformations in Physics and their Application to Acoustics. Scientific Reports, 3(1). doi:10.1038/srep02009García-Meca, C., Carloni, S., Barceló, C., Jannes, G., Sánchez-Dehesa, J., & Martínez, A. (2014). Space–time transformation acoustics. Wave Motion, 51(5), 785-797. doi:10.1016/j.wavemoti.2014.01.008Kinsler, P., & McCall, M. W. (2014). Transformation devices: Event carpets in space and space-time. Physical Review A, 89(6). doi:10.1103/physreva.89.063818Kinsler, P., & McCall, M. W. (2013). Cloaks, editors, and bubbles: applications of spacetime transformation theory. Annalen der Physik, 526(1-2), 51-62. doi:10.1002/andp.201300164Leonhardt, U., & Philbin, T. G. (2006). General relativity in electrical engineering. New Journal of Physics, 8(10), 247-247. doi:10.1088/1367-2630/8/10/247Guenneau, S., & Puvirajesinghe, T. M. (2013). Fick’s second law transformed: one path to cloaking in mass diffusion. Journal of The Royal Society Interface, 10(83), 20130106. doi:10.1098/rsif.2013.0106Guenneau, S., Petiteau, D., Zerrad, M., Amra, C., & Puvirajesinghe, T. (2015). Transformed Fourier and Fick equations for the control of heat and mass diffusion. AIP Advances, 5(5), 053404. doi:10.1063/1.4917492García-Meca, C., Carloni, S., Barceló, C., Jannes, G., Sánchez-Dehesa, J., & Martínez, A. (2014). Analogue transformation acoustics and the compression of spacetime. Photonics and Nanostructures - Fundamentals and Applications, 12(4), 312-318. doi:10.1016/j.photonics.2014.05.001Schittny, R., Kadic, M., Buckmann, T., & Wegener, M. (2014). Invisibility cloaking in a diffusive light scattering medium. Science, 345(6195), 427-429. doi:10.1126/science.1254524Chester, M. (1963). Second Sound in Solids. Physical Review, 131(5), 2013-2015. doi:10.1103/physrev.131.2013Ali, Y. M., & Zhang, L. C. (2005). Relativistic heat conduction. International Journal of Heat and Mass Transfer, 48(12), 2397-2406. doi:10.1016/j.ijheatmasstransfer.2005.02.003López Molina, J. A., Rivera, M. J., & Berjano, E. (2014). Fourier, hyperbolic and relativistic heat transfer equations: a comparative analytical study. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 470(2172), 20140547. doi:10.1098/rspa.2014.0547Christov, C. I., & Jordan, P. M. (2005). Heat Conduction Paradox Involving Second-Sound Propagation in Moving Media. Physical Review Letters, 94(15). doi:10.1103/physrevlett.94.154301Cho, J., Losego, M. D., Zhang, H. G., Kim, H., Zuo, J., Petrov, I., … Braun, P. V. (2014). Electrochemically tunable thermal conductivity of lithium cobalt oxide. Nature Communications, 5(1). doi:10.1038/ncomms5035Ihlefeld, J. F., Foley, B. M., Scrymgeour, D. A., Michael, J. R., McKenzie, B. B., Medlin, D. L., … Hopkins, P. E. (2015). Room-Temperature Voltage Tunable Phonon Thermal Conductivity via Reconfigurable Interfaces in Ferroelectric Thin Films. Nano Letters, 15(3), 1791-1795. doi:10.1021/nl504505

Scalar Casimir Effect on a D-dimensional Einstein Static Universe

We compute the renormalised energy momentum tensor of a free scalar field coupled to gravity on an (n+1)-dimensional Einstein Static Universe (ESU), RxS^n, with arbitrary low energy effective operators (up to mass dimension n+1). A generic class of regulators is used, together with the Abel-Plana formula, leading to a manifestly regulator independent result. The general structure of the divergences is analysed to show that all the gravitational couplings (not just the cosmological constant) are renormalised for an arbitrary regulator. Various commonly used methods (damping function, point-splitting, momentum cut-off and zeta function) are shown to, effectively, belong to the given class. The final results depend strongly on the parity of n. A detailed analytical and numerical analysis is performed for the behaviours of the renormalised energy density and a quantity `sigma' which determines if the strong energy condition holds for the `quantum fluid'. We briefly discuss the quantum fluid back-reaction problem, via the higher dimensional Friedmann and Raychaudhuri equations, observe that equilibrium radii exist and unveil the possibility of a `Casimir stabilisation of Einstein Static Universes'.Comment: 37 pages, 15 figures, v2: minor changes in sections 1, 2.5, 3 and 4; version published in CQ

Analog gravity from field theory normal modes?

We demonstrate that the emergence of a curved spacetime ``effective Lorentzian geometry'' is a common and generic result of linearizing a field theory around some non-trivial background. This investigation is motivated by considering the large number of ``analog models'' of general relativity that have recently been developed based on condensed matter physics, and asking whether there is something more fundamental going on. Indeed, linearization of a classical field theory (a field theoretic ``normal mode analysis'') results in fluctuations whose propagation is governed by a Lorentzian-signature curved spacetime ``effective metric''. For a single scalar field, this procedure results in a unique effective metric, which is quite sufficient for simulating kinematic aspects of general relativity (up to and including Hawking radiation). Quantizing the linearized fluctuations, the one-loop effective action contains a term proportional to the Einstein--Hilbert action, suggesting that while classical physics is responsible for generating an ``effective geometry'', quantum physics can be argued to induce an ``effective dynamics''. The situation is strongly reminiscent of Sakharov's ``induced gravity'' scenario, and suggests that Einstein gravity is an emergent low-energy long-distance phenomenon that is insensitive to the details of the high-energy short-distance physics. (We mean this in the same sense that hydrodynamics is a long-distance emergent phenomenon, many of whose predictions are insensitive to the short-distance cutoff implicit in molecular dynamics.)Comment: Revtex 4 (beta 5); 12 pages in single-column forma

Are isomeric alkenes used in species recognition among neo-tropical stingless bees (Melipona spp)

The majority of our understanding of the role of cuticular hydrocarbons (CHC) in recognition is based largely on temperate ant species and honey bees. The stingless bees remain relatively poorly studied, despite being the largest group of eusocial bees, comprising more than 400 species in some 60 genera. The Meliponini and Apini diverged between 80-130 Myr B.P. so the evolutionary trajectories that shaped the chemical communication systems in ants, honeybees and stingless bees may be very different. Therefore, the main aim of this study was to study if a unique species CHC signal existed in Neotropical stingless bees, as shown for many temperate species, and if so what compounds are involved. This was achieved by collecting CHC data from 24 colonies belonging to six species of Melipona from North-eastern Brazil and comparing this new data with all previously published CHC studies on Melipona. We found that each of the eleven Melipona species studied so far each produced a unique species CHC signal based around their alkene isomer production. A remarkable number of alkene isomers, up to 25 in M. asilvai, indicated the diversification of alkene positional isomers among the stingless bees. The only other group to have really diversified in alkene isomer production are the primitively eusocial Bumblebees (Bombus spp), which are the sister group of the stingless bees. Furthermore, among the eleven Neotropical Melipona species we could detect no effect of the environment on the proportion of alkane production as has been suggested for some other species

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Search for direct top-squark pair production in final states with two leptons in pp collisions at √s = 8TeV with the ATLAS detector

A search is presented for direct top-squark pair production in final states with two leptons (electrons or muons) of opposite charge using 20.3 fb−1 of pp collision data at √s = 8 TeV, collected by the ATLAS experiment at the Large Hadron Collider in 2012. No excess over the Standard Model expectation is found. The results are interpreted under the separate assumptions (i) that the top squark decays to a b-quark in addition to an on-shell chargino whose decay occurs via a real or virtual W boson, or (ii) that the top squark decays to a t-quark and the lightest neutralino. A top squark with a mass between 150 GeV and 445 GeV decaying to a b-quark and an on-shell chargino is excluded at 95% confidence level for a top squark mass equal to the chargino mass plus 10 GeV, in the case of a 1 GeV lightest neutralino. Top squarks with masses between 215 (90) GeV and 530 (170) GeV decaying to an on-shell (off-shell) t-quark and a neutralino are excluded at 95% confidence level for a 1 GeV neutralino

Search for top squark pair production in final states with one isolated lepton, jets, and missing transverse momentum in √s = 8 TeV pp collisions with the ATLAS detector

The results of a search for top squark (stop) pair production in final states with one isolated lepton, jets, and missing transverse momentum are reported. The analysis is performed with proton-proton collision data at s√ = 8 TeV collected with the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of 20 fb−1. The lightest supersymmetric particle (LSP) is taken to be the lightest neutralino which only interacts weakly and is assumed to be stable. The stop decay modes considered are those to a top quark and the LSP as well as to a bottom quark and the lightest chargino, where the chargino decays to the LSP by emitting a W boson. A wide range of scenarios with different mass splittings between the stop, the lightest neutralino and the lightest chargino are considered, including cases where the W bosons or the top quarks are off-shell. Decay modes involving the heavier charginos and neutralinos are addressed using a set of phenomenological models of supersymmetry. No significant excess over the Standard Model prediction is observed. A stop with a mass between 210 and 640 GeV decaying directly to a top quark and a massless LSP is excluded at 95% confidence level, and in models where the mass of the lightest chargino is twice that of the LSP, stops are excluded at 95% confidence level up to a mass of 500 GeV for an LSP mass in the range of 100 to 150 GeV. Stringent exclusion limits are also derived for all other stop decay modes considered, and model-independent upper limits are set on the visible cross-section for processes beyond the Standard Model

Search for direct top squark pair production in events with a Z boson, b-jets and missing transverse momentum in s √ = 8 TeV pp collisions with the ATLAS detector

A search is presented for direct top squark pair production using events with at least two leptons including a same-flavour opposite-sign pair with invariant mass consistent with the Z boson mass, jets tagged as originating from b-quarks and missing transverse momentum. The analysis is performed with proton–proton collision data at s√=8 TeV collected with the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of 20.3 fb−¹. No excess beyond the Standard Model expectation is observed. Interpretations of the results are provided in models based on the direct pair production of the heavier top squark state (t~2) followed by the decay to the lighter top squark state (t~1) via t~2→Zt~1, and for t~1 pair production in natural gauge-mediated supersymmetry breaking scenarios where the neutralino (χ~10) is the next-to-lightest supersymmetric particle and decays producing a Z boson and a gravitino (G~) via the χ~10→ZG~ process

Search for supersymmetry in events with large missing transverse momentum, jets, and at least one tau lepton in 20 fb−1 of √s=8 TeV proton-proton collision data with the ATLAS detector

A search for supersymmetry (SUSY) in events with large missing transverse momentum, jets, at least one hadronically decaying tau lepton and zero or one additional light leptons (electron/muon), has been performed using 20.3fb−1 of proton-proton collision data at √s= 8 TeV recorded with the ATLAS detector at the Large Hadron Collider. No excess above the Standard Model background expectation is observed in the various signal regions and 95% confidence level upper limits on the visible cross section for new phenomena are set. The results of the analysis are interpreted in several SUSY scenarios, significantly extending previous limits obtained in the same final states. In the framework of minimal gauge-mediated SUSY breaking models, values of the SUSY breaking scale Λ below 63 TeV are excluded, independently of tan β. Exclusion limits are also derived for an mSUGRA/CMSSM model, in both the R-parity-conserving and R-parity-violating case. A further interpretation is presented in a framework of natural gauge mediation, in which the gluino is assumed to be the only light coloured sparticle and gluino masses below 1090 GeV are excluded