Particle Physics

We investigate the one-parameter Calabi-Yau models and identify families of D5-branes which are associated to lines embedded in these manifolds. The moduli spaces are given by sets of Riemann curves, which form a web whose intersection points are described by permutation branes. We arrive at a geometric interpretation for bulk-boundary correlators as holomorphic differentials on the moduli space and use this to compute effective open-closed superpotentials to all orders in the open string couplings. The fixed points of D5-brane moduli under bulk deformations are determined.

Uncertainty may be an important component of the motivation provided by
learning games, especially when associated with gaming rather than learning. Three studies
are reported that explore the influence of gaming uncertainty on engagement with computer-
based learning games. In the first study, children (10–11 years) played a simple
maths quiz. Participants chose their preferred reward for a correct answer prior to seeing
each question. They could either receive a single point or toss an animated coin to receive 2
points for heads or none for tails. A preference for the uncertain option was revealed and
this increased during the quiz. The second study explored the discourse around learning
when pairs of participants (13–14 years) competed against the computer in a science quiz.
Progress depended on the acquisition of facts but also on the outcomes of throwing dice.
Discourse was characterised by a close intermingling of learning and gaming talk without
salient problematic constructions regarding fairness when losing points due to gaming
uncertainty. A final experiment explored whether, in this type of game, the uncertainty
provided by the gaming component could influence players’ affective response to the
learning component. Electrodermal activity (EDA) of 16 adults was measured while they
played the quiz with and without the element of chance provided by the dice. Results
showed EDA when answering questions was increased by inclusion of gaming uncertainty.
Findings are discussed in terms of the potential benefits of combining gaming uncertainty
with learning and directions for further research in this area are outlined.

The concept of “social capital” has been spreading in the last years in planning studies, in order to define and quantify the relationships between individuals (or groups and organisations) which can bring to an increase of public value in community contexts. However, such a field of analysis is still in need of improvements in both terminological and methodological terms. In particular, very few attempts have been made in order to classify the single dimensions of social capital with regard to its supposed benefits, in particular to the sharing of knowledge, which is widely considered as one of the main ‘public value’ components. This paper is aimed at providing a conceptual attempt at a cognitive – based classification of social capital, inspired by Nahapiet and Ghoshal’s work (1998), and by a reflection on the dimensions of transmittable knowledge, identified on the basis of organisational and knowledge management literature, and on the barriers which affect sharing processes. The paper is aimed at providing a conceptual framework and some guidelines which might be helpful in order to define and implement planning and development strategies based on a participative and inclusive approach and able to exploit the capacity that social connections can have in supporting virtuous processes.

A nonrelativistic particle on a circle and subject to a cos^{-2}(k phi) potential is related to the two-dimensional (dihedral) Coxeter system I_2(k), for k in N. For such `dihedral systems' we construct the action-angle variables and establish a local equivalence with a free particle on the circle. We perform the quantization of these systems in the action-angle variables and discuss the supersymmetric extension of this procedure. By allowing radial motion one obtains related two-dimensional systems, including A_2, BC_2 and G_2 three-particle rational Calogero models on R, which we also analyze.

It is shown that for a central potential that is an injective function of the radial coordinate, a second central potential can be found that leads to trajectories in the configuration space and the momentum space coinciding, respectively, with the trajectories in the momentum space and the configuration space produced by the original potential.

This paper shows a novel method for predicting the onset of acoustically driven combustion instabilities in gas turbine combustors. The basic idea is that the governing equations of the acoustic waves can be coupled with a flame heat release model and solved in the frequency domain. The paper shows that a complex eigenvalue problem is obtained that can be solved numerically by implementing the governing equations in
the “Acoustic” module of COMSOL Multiphysics. The procedure allows one to identify the frequencies at which thermoacoustic instabilities are expected and the growth rate of the pressure oscillations, at the onset of instability, when the hypothesis of linear behaviour of the acoustic waves can be applied.

We point out that the exchange of a Goldstone pseudo-scalar can provide an enhancement in the dark matter annihilation rate capable of explaining the excess flux seen in high energy cosmic ray data. The mechanism of enhancement involves the coupling of s and d waves through the tensor force that is very strong and, in fact, singular at short distances. The results indicate that large enhancements require some amount of fine tuning. We also discuss the enhancement due to other singular attractive potentials, such as WIMP models with a permanent electric dipole.

The subatomic particle mass spectrum in the 100 MeV to 7,000 MeV range is retrodicted to a first approximation using the Kerr solution of General Relativity.  The particle masses appear to form a restricted set of quantized values of the Kerr solution: n1/2 M, where values of n are a set of discrete integers and M is the revised Planck mass.  The accuracy of the 27 retrodicted masses averages 98.4%.  Discrete Scale Relativity is required to evaluate M, which differs from the conventional Planck mass by a factor of roughly 1019.

After an introduction to some basic issues in non-commutative geometry (Gel'fand duality, spectral triples), we present a "panoramic view" of the status of our current research program on the use of categorical methods in the setting of A.Connes' non-commutative geometry: morphisms/categories of spectral triples, categorification of Gel'fand duality. We conclude with a summary of the expected applications of "categorical non-commutative geometry" to structural questions in relativistic quantum physics: (hyper)covariance, quantum space-time, (algebraic) quantum gravity.

"PDF file: http://dml.riken.jp/pub/nori/pdf/J_Phys_C_C_113_21218_2009.pdf .


We theoretically examine the light-to-electricity energy conversion in a molecular triad coupled to conducting leads. This coupling allows us to drive a current through the system. We derive the equations of motion for the electron density operators and determine the dependence of the current, quantum yield, and thermodynamic efficiency on temperature, the electrochemical potentials of the leads, as well as on the light intensity and frequency of the external electromagnetic field. For the molecular triad consisting of ferrocene, porphyrin, and fullerene molecules, we find that, in the case of relatively strong coupling to the leads, the power-conversion efficiency can exceed 40% and the quantum yield can be more than 90%, instead of the 25% quantum yield observed in experiments. Thus, this system is highly attractive for solar cell applications. The large predicted increase in the efficiency of this system is due to the stronger coupling to the contacts, which allows the triad to move more electrons through it, absorbing more photons per unit time, and doing more work."

We provide combinatorial as well as probabilistic interpretations for the q-analogue of the Pochhammer k-symbol introduced by Diaz and Teruel. We introduce q-analogues of the Mellin transform in order to study the q-analogue of the k-gamma distribution.

The difference between a Klein-Gordon random field and the complex Klein-Gordon quantum field is characterized, explicitly comparing the rôles played by negative frequency modes of test functions in creation and annihilation operator presentations of the two theories. The random field and the complex quantum field can both be constructed from the same creation and annihilation operator algebra, making them equivalent in that sense.

This must be one of the very few peer reviewed and reputably published technical papers to have been written entirely in rhyming verse. The subject matter concerns the physics of a macroscopic quantum system.

No case is known of a mass flow exhibiting diffraction. A fluid flowing through a grid shows no interference effects. Atoms or light passing through a grid do show interference. Because of its macroscopic quantum nature the possibility of just such an interference effect could exist for superfluid helium flow. The experiment was an attempt to see diffraction in liquid helium.  The paper explains, entirely in rhyme, the theory behind the expectation and all the technical details of the experiment. Unfortunately, no diffraction was observed.

The scale invariance of the source-free Einstein field equations suggests that one might be able to model hadrons as “strong gravity” black holes, if one uses an appropriate rescaling of units or a revised gravitational coupling factor.  The inner consistency of this hypothesis is tested by retrodicting a close approximation to the mass of the proton from an equation that relates the angular momentum and mass of a Kerr black hole.  More accurate mass and radius values for the proton are then retrodicted using the geometrodynamic form of the full Kerr-Newman solution of the Einstein-Maxwell equations.  The radius of an alpha particle is calculated as an additional retrodictive test.  In a third retrodictive test of the “strong gravity” hypothesis, the subatomic particle mass spectrum in the 100 MeV to 7,000 MeV range is retrodicted to a first approximation using the Kerr solution of General Relativity.  The particle masses appear to form a restricted set of quantized values of the Kerr solution: (sqrt n)(M), where values of n are a set of discrete integers and M is the revised Planck mass.  The accuracy of the 27 retrodicted masses averages 98.4%.  Finally, the new atomic scale gravitational coupling constant suggests a radical revision of the assumptions governing the Planck scale, and leads to a natural explanation for the fine structure constant.

The generalized Einstein action is treated quantum mechanically by using a quadratic lagrangian form. The canonical quantization of this action is obtained by using the auxiliary variable to define the generalized momentum. Physical constraints are imposed on the surface term, which is defined to be the cosmological constant. One obtains the familiar Wheeler-de Witt equation. The solution of this equation is in conformity with General Relativity (GR) .In addition to the fact that it is free from GR setbacks at the early universe, since it gives time decaying cosmological constant. The wave function of the universe and the cosmic scale factor are complex quantities, which indicates the existance of quantum effects.2.7k, CBR temperature is calculated.

Particle accelerators are the tools that physicists use today in order to probe the fundamental forces of Nature, by accelerating charged particles such as electrons and protons to high energies and then smashing them together. For the past 70 years the acceleration schemes have been based on the same technology, which is to place the particles onto radio-frequency electric fields inside metallic cavities. However, since the accelerating gradients cannot be increased arbitrarily due to limiting effects such as wall breakdown, in order to reach higher energies today’s accelerators require km-long structures that have become very expensive to built, and therefore novel accelerating techniques are needed to push the energy frontier further.
        Plasmas do not suffer from those limitations since they are gases that are already broken down into electrons and ions. In addition, the collective behavior of the particles in plasmas allows for generated accelerating electric fields that are orders of magnitude larger than those available in conventional accelerators. Such wakefields have been demonstrated experimentally, typically by feeding either single electron bunches or laser beams into high density plasmas. As such plasma acceleration technologies mature, one of the main future challenges is to monoenergetically accelerate a second trailing bunch by multiplying its energy in an efficient manner, so that it can potentially be used in a future particle collider.
        The work presented in this dissertation is a fruitful combination of theory, simulations and experiments that analyzes the use of multiple electron bunches in order to enhance certain plasma acceleration schemes. Specifically, the acceleration of a trailing electron bunch in a high-gradient wakefield driven by a preceding bunch is demonstrated experimentally for the first time by using bunches short enough to sample a small phase of the plasma wakes. Additionally, it is found through theoretical analysis and through simulations that by using multiple bunches to drive the wakefields, the energy of a trailing bunch could be efficiently multiplied in a single stage, thus possibly reducing the total length of the accelerator to a more manageable scale. Relevant proof-of-principle experimental results are also presented, along with suggested designs that could be tested in the near future. Furthermore, electron beam and plasma diagnostics are analyzed and presented, which are necessary for properly completing and understanding any plasma wakefield experiment. Finally, certain types of plasma sources that can be used in related experiments are designed, diagnosed and tested in detail.

The theoretical vacuum energy density estimated on the basis of the Standard Model of particle physics and very general quantum assumptions is 59 to 123 orders of magnitude larger than the measured vacuum energy density for the observable universe which is determined on the basis of the Standard Model of cosmology and empirical data.  This enormous disparity between the expectations of two of our most widely accepted theoretical frameworks demands a credible and self-consistent explanation, and yet even after decades of sporadic effort a generally accepted resolution of this crisis has not surfaced.  Very recently, however, a discrete self-similar cosmological paradigm based on the fundamental principle of discrete scale invariance has been found to offer a rationale for reducing the vacuum energy density disparity by at least 115 orders of magnitude, and possibly this new paradigm offers a means of eliminating the vacuum energy density crisis entirely.

This book addresses the question: why do more girls than boys choose to continue studying mathematics in England? It discusses the issue using interviews with young people aged 16-19 who did choose to continue with mathematics. It uses a feminist post-structural framework.

The book is published by Open University Press.

We are building up a light scattering setup at the Instituto de Astrofísica de Andalucía (IAA), Granada, Spain. The design of this new setup is based on the well known apparatus currently located at the Astronomical Institute "Anton Pannekoek", University of Amsterdam, The Neteherlands [1],[2]. By using a polarization modulation technique, all scattering matrix elements as function of the scattering angle are obtained from 8 separate measurement runs. In this new setup we use an Argon-Kripton laser (483 nm, 488 nm, 514 nm, 568 nm, and 647 nm) as light source. The detectors are mounted on dove tails that allow their movement backward and forward. In addition, the detectors have been designed to minimize blockage of the laser beam at positions close to the forward and backward directions. In this way we intend to do measurements covering an angle range from 3 to 177 degrees. The alignment of the optics is automatically done and controlled from the computer reducing the measurement time.

We initiate a study of Hilbert modules over the polynomial algebra A=C [z_1,...,z_d] that are obtained by completing A with respect to an inner product having certain natural properties. A standard Hilbert module is a finite multiplicity version of one of these. Standard Hilbert modules occupy a position analogous to that of free modules of finite rank in commutative algebra, and their quotients by submodules give rise to universal solutions of nonlinear relations.

We consider an example of strongly non-local interaction in incompressible magnetohydrodynamic (MHD) turbulence which corresponds to the case where the Alfvén waves travelling in the opposite directions have essentially different characteristic wavelengths. We use two approaches to the dynamics of turbulent Alfvénic wavepackets: the first is a geometrical WKB theory [Phys. Lett. A 165 (1992) 330] and the second one is a three-wave kinetic equation derived for weakly turbulent waves [J. Plasma Phys., in press]. We show that these theories have a common limit of weak turbulence with scale separation in which they both predict the same Fokker-Planck equation for the wave power spectrum. In both cases the packet wavenumbers (and therefore the Lagrangian field-line separations) are allowed to experience order 1 changes. The WKB theory developed here formalises an intuitive geometrical argument of Goldreich and Sridhar [ApJ 485 (1997) 680] and allows one to see where such an intuition leads to a wrong conclusion about the inapplicability of the three-wave kinetic equation for order 1 wavepacket distortions. We show that the exponent of the constant flux non-local spectrum matches the value previously found for local turbulence at the boundary of the locality interval. The relationship between the WKB theory and the weak turbulence theory found in this paper for an ensemble of Alfvén waves seems to be general for three-wave systems.

This Letter demonstrates that the kinetic equations for wave turbulence, the long time statistical behavior of a sea of weakly coupled, dispersive waves, will almost always develop solutions for which the theory fails due to strongly nonlinear and intermittent events either at small or large scales.  (A.C. Newell). 0375-9601/01/$ -see front matter  2001 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 5 -9 6 0 1 ( 0 1 ) 0 0 0 1 6 -0

We report a numerical study of turbulence and Bose-Einstein condensation within the two-dimensional Gross-Pitaevsky model with repulsive interaction. In the presence of weak forcing localized around some wave number in the Fourier space, we observe three qualitatively different evolution stages. At the initial stage a thermodynamic energy equipartition spectrum forms at both smaller and larger scales with respect to the forcing scale. This agrees with predictions of the four-wave kinetic equation of the Wave Turbulence (WT) theory. At the second stage, WT breaks down at large scales and the interactions become strongly nonlinear. Here, we observe formation of a gas of quantum vortices whose number decreases due to an annihilation process helped by the acoustic component. This process leads to formation of a coherent-phase Bose-Einstein condensate. After such a coherent-phase condensate forms, evolution enters a third stage characterised by three-wave interactions of acoustic waves that can be described again using the WT theory.