Closed String Amplitudes from Gauge Fixed String Field Theory

Closed string diagrams are derived from cubic open string field theory using a gauge fixed kinetic operator. The basic idea is to use a string propagator that does not generate a boundary to the world sheet. Using this propagator and the closed string vertex, the moduli space of closed string surfaces is covered, so closed string scattering amplitudes should be reproduced. This kinetic operator could be a gauge fixed form of the string field theory action around the closed string vacuum.Comment: 10 pages, revtex, 3 figures. Discussion on the covering of moduli expanded, version to appear in PR

Peripheral and central inputs shape network dynamics in the developing visual cortex in vivo

Spontaneous network activity constitutes a central theme during the development of neuronal circuitry [1, 2]. Before the onset of vision, retinal neurons generate waves of spontaneous activity that are relayed along the ascending visual pathway [3, 4] and shape activity patterns in these regions [5, 6]. The spatiotemporal nature of retinal waves is required to establish precise functional maps in higher visual areas, and their disruption results in enlarged axonal projection areas (e.g., [7-10]). However, how retinal inputs shape network dynamics in the visual cortex on the cellular level is unknown. Using in vivo two-photon calcium imaging, we identified two independently occurring patterns of network activity in the mouse primary visual cortex (V1) before and at the onset of vision. Acute manipulations of spontaneous retinal activity revealed that one type of network activity largely originated in the retina and was characterized by low synchronicity (L-) events. In addition, we identified a type of high synchronicity (H-) events that required gap junction signaling but were independent of retinal input. Moreover, the patterns differed in wave progression and developmental profile. Our data suggest that different activity patterns have complementary functions during the formation of synaptic circuits in the developing visual cortex

Dynamics with Infinitely Many Time Derivatives and Rolling Tachyons

Both in string field theory and in p-adic string theory the equations of motion involve infinite number of time derivatives. We argue that the initial value problem is qualitatively different from that obtained in the limit of many time derivatives in that the space of initial conditions becomes strongly constrained. We calculate the energy-momentum tensor and study in detail time dependent solutions representing tachyons rolling on the p-adic string theory potentials. For even potentials we find surprising small oscillations at the tachyon vacuum. These are not conventional physical states but rather anharmonic oscillations with a nontrivial frequency--amplitude relation. When the potentials are not even, small oscillatory solutions around the bottom must grow in amplitude without a bound. Open string field theory resembles this latter case, the tachyon rolls to the bottom and ever growing oscillations ensue. We discuss the significance of these results for the issues of emerging closed strings and tachyon matter.Comment: 46 pages, 14 figures, LaTeX. Replaced version: Minor typos corrected, some figures edited for clarit

A twistor-like D=10 superparticle action with manifest N=8 world-line supersymmetry

We propose a new formulation of the $D=10$ Brink-Schwarz superparticle which is manifestly invariant under both the target-space super-Poincar\'e group and the world-line local $N=8$ superconformal group. This twistor-like construction naturally involves the sphere $S^8$ as a coset space of the $D=10$ Lorentz group. The action contains only a finite set of auxiliary fields, but they appear in unusual trilinear combinations. The origin of the on-shell $D=10$ fermionic $\kappa$ symmetry of the standard Brink-Schwarz formulation is explained. The coupling to a $D=10$ super-Maxwell background requires a new mechanism, in which the electric charge appears only on shell as an integration constant.Comment: 22pages, standard LATEX fil

A framework for the systematic implementation of Green-Lean and sustainability in SMEs

Evidence suggests that smaller organisations find the implementation of combined operations- and environmental Sustainability improvement initiatives such as Green-Lean and Sustainability (GLS) challenging. This paper, therefore, develops a framework for the systematic implementation of Green-Lean and Sustainability in small and medium-sized enterprises (SMEs) to achieve long-term improvement of environmental, social and economic processes and performance. A literature assessment of theories, frameworks, and concepts was employed in the study to better comprehend the difficulties confronting the modern business world. In addition, the research employed expert perspectives from the lean, green-lean, and sustainability fields to propose, develop, test, and validate a framework for addressing business concerns. The research uncovers considerable implementation problems, such as employee motivation and integration, responsibilities, and measurements. It also underlines the success factors for the implementation process, such as management, firm- goals and strategy, reviews and audits, vision, and guidance by lean, green and sustainability frameworks. The novelty in this research lies in the approach where Green-Lean and Sustainability are combined and applied in an SME context. The presented framework offers the potential to be implemented in SMEs that operate in different sectors and contexts and are affected by different environmental and social considerations

A Twistor Formulation of the Non-Heterotic Superstring with Manifest Worldsheet Supersymmetry

We propose a new formulation of the $D=3$ type II superstring which is manifestly invariant under both target-space $N=2$ supersymmetry and worldsheet $N=(1,1)$ super reparametrizations. This gives rise to a set of twistor (commuting spinor) variables, which provide a solution to the two Virasoro constraints. The worldsheet supergravity fields are shown to play the r\^ole of auxiliary fields.Comment: 21p., LaTe

Thermal conditions affecting heat transfer in FDM/FFE: a contribution towards the numerical modelling of the process

The performance of parts produced by Free Form Extrusion (FFE), an increasingly popular additive manufacturing technique, depends mainly on their dimensional accuracy, surface quality and mechanical performance. These attributes are strongly influenced by the evolution of the filament temperature and deformation during deposition and solidification. Consequently, the availability of adequate process modelling software would offer a powerful tool to support efficient process set-up and optimisation. This work examines the contribution to the overall heat transfer of various thermal phenomena developing during the manufacturing sequence, including convection and radiation with the environment, conduction with support and between adjacent filaments, radiation between adjacent filaments and convection with entrapped air. The magnitude of the mechanical deformation is also studied. Once this exercise is completed, it is possible to select the material properties, process variables and thermal phenomena that should be taken in for effective numerical modelling of FFE.This work was supported by Strategic Project - LA 25 - 2013–2014 [PEst-C/CTM/LA0025/2013]

Supergravity interacting with bosonic p-branes and local supersymmetry

We study the coupling of supergravity with a purely bosonic brane source (bosonic p-brane). The interaction, described by the sum of their respective actions, is self-consistent if the bosonic p-brane is the pure bosonic limit of a super-p-brane. In that case the dynamical system preserves 1/2 of the local supersymmetry characteristic of the `free' supergravity.Comment: 11 pages, RevTe

Huyghens Principle, Planck Law: Peculiarities in the Behavior of Planar Photons

Huyghens principle and Planck law are studied in Maxwell and Maxwell-Chern-Simons frameworks in (2+1) dimensions. Contrary to (3+1) dimensions, massless photons are shown to violate Huyghens principle in planar world. In addition, we obtain that Planck law is no longer proportional to $\nu^3$, but to the squared frequency, $\nu^2$, of the planar photons. We also briefly discuss possible physical consequences of these results.Comment: 10 pages, no figures. Latex forma

Baryon polarization in low-energy unpolarized meson-baryon scattering

We compute the polarization of the final-state baryon, in its rest frame, in low-energy meson--baryon scattering with unpolarized initial state, in Unitarized BChPT. Free parameters are determined by fitting total and differential cross-section data (and spin-asymmetry or polarization data if available) for $pK^-$, $pK^+$ and $p\pi^+$ scattering. We also compare our results with those of leading-order BChPT