11115006
Environmental adaptability and mutants: Exploring new concepts in particle transport for multi-scale simulation
Ongoing investigations to introduce software techniques suitable to support new experimental requirements for multi-scale simulation are discussed.
121149545
Generalization and Interpretation of Dirac's Positive-Energy Relativistic Wave Equation
We generalize Dirac's new equation so as to deacribe particles of mass m and arbitrary spin s. The same remarkable properties are found: positive energy, non-negative density, a conserved four-vector current, and the impossibility of minimal electromagnetic interaction. We show that the particles described by a subset of these equations are composites of two subparticles interacting by a relativistic action-at-a-distance interaction charactcrized by two harmonic oscillators. For these composite particles we find a linear relation between the square of the mass and the spin. We emphasizr that the essential content of the generalized new Dirac equation is that it constitutes an example of a convariant solution for two interacting particles, and provides an explicit examaple of a new quantal subdynamics distinct from the (classical) front relativistic dynamics of Dirac. (auth)
121268649
Comment on "Stigma of a Dirac Particle in an Even Environment"
121155180
DYON THREE-TRIPLET MODEL OF HADRONS.
118337761
Manifest dyality invariance in electrodynamics and the cabibbo-ferrari theory of magnetic monopoles
SummaryOne of the intrinsic symmetry properties of the Maxwell-Lorentz theory of electrodynamics is the invariance of the theory under « dyality » transformation, that is, a dual transformation on fieldsand sourcessimultaneously. In this paper we give a manifestly dyality-invariant formulation of electrodynamics. This is done by expressing the electromagnetic-field tensors in terms of an antisymmetric tensor of rank two, called a Hertz tensor, consisting of electric and magnetic Hertz vector potentials. An equation is derived which relates the electromagnetic fields when sources consist of electric charges only, magnetic charges only, and both. The present formalism provides a natural physical basis for the Cabibbo-Ferrari theory in which two four-vector potentials and a mixed gauge transformation between them are introduced.RiassuntoUna delle proprietà di simmetria intrinseca della teoria di Maxwell-Lorentz dell’elettrodinamica è l’invarianza della teoria rispetto alle trasformazioni di «dialità», cioè una trasformazione duale sui campie le sorgenticontemporaneamente. In questo articolo si espone una formulazione dell’elettrodinamica che è manifestamente invariante rispetto alla dialità. Si fà ciò esprimendo i tensori del campo elettromagnetico in termini di un tensore antisimmetrico di rango due, detto tensore di Hertz, consistente di potenziali del vettore di Hertz elettrico e magnetico. Si deduce un’equazione che mette in relazione i campi magnetici quando le sorgenti consistono di sole cariche elettriche, di sole cariche magnetiche, o di entrambe. Questo formalismo fornisce una naturale base fisica per la teoria di Cabibbo-Ferrari, in cui si introducono due potenziali quadrivettori e una trasformazione di gauge mista tra essi.РеэюмеОдно иэ свойств внутренней симметрии Максвелл-Лорентцевс кой теории злектродинамики представляет инвариантность теории относительно преобраэования «диальности», т.е. одновременное дуальное преобраэование полей и источников. В зтой статье мы приводим формулировку злектродинамики, обладаюшую явной диальной инвариантностью. Это достигается эа счет выражения тенэора злектромагнитного поля череэ антисимметричный тенэор второго ранга, наэываемый тенэором Герца, который состоит иэ злектрического и магнитного векторных потенциалов Герца. Выводится уравнение, которое свяэывает злектромагнитные поля, когда источники состоят только иэ злектрических эарядов, только иэ магнитных эарядов и тех и других. Предлагаемый формалиэм обеспечивает естественную фиэическую основу для теории Кабиббо-Феррари, в которой вводятся два четырех-векторных потенциала и смещанное калибровочное преобраэование между ними.
120561444
Comment on the paper entitled «On the Poincaré noninvariance of a recent alternative to the Dirac equation»
119655234
On spinfoam models in large spin regime
We study the semiclassical behavior of Lorentzian Engle–Pereira–Rovelli–Livine (EPRL) spinfoam model, by taking into account the sum over spins in the large spin regime. We also employ the method of stationary phase analysis with parameters and the so-called, almost analytic machinery, in order to find the asymptotic behavior of the contributions from all possible large spin configurations in the spinfoam model. The spins contributing the sum are written as Jf = λjf, where λ is a large parameter resulting in an asymptotic expansion via stationary phase approximation. The analysis shows that at least for the simplicial Lorentzian geometries (as spinfoam critical configurations), they contribute the leading order approximation of spinfoam amplitude only when their deficit angles satisfy mod . Our analysis results in a curvature expansion of the semiclassical low energy effective action from the spinfoam model, where the UV modifications of Einstein gravity appear as subleading high-curvature corrections.
119144559
Cosmological Constant in LQG Vertex Amplitude
A new q-deformation of the Euclidean EPRL/FK vertex amplitude is proposed by using the evaluation of the Vassiliev invariant associated with a 4-simplex graph (related to two copies of quantum SU(2) group at different roots of unity) embedded in a 3-sphere. We show that the large-j asymptotics of the q-deformed vertex amplitude gives the Regge action with a cosmological constant. In the end we also discuss its relation with a Chern-Simons theory on the boundary of 4-simplex.
118178605
SL(2,C) Chern–Simons theory, a non-planar graph operator, and 4D quantum gravity with a cosmological constant: Semiclassical geometry
Abstract We study the expectation value of a nonplanar Wilson graph operator in SL ( 2 , C ) Chern–Simons theory on S 3 . In particular we analyze its asymptotic behavior in the double-scaling limit in which both the representation labels and the Chern–Simons coupling are taken to be large, but with fixed ratio. When the Wilson graph operator has a specific form, motivated by loop quantum gravity, the critical point equations obtained in this double-scaling limit describe a very specific class of flat connection on the graph complement manifold. We find that flat connections in this class are in correspondence with the geometries of constant curvature 4-simplices. The result is fully non-perturbative from the perspective of the reconstructed geometry. We also show that the asymptotic behavior of the amplitude contains, at the leading order, an oscillatory part proportional to the Regge action for the single 4-simplex in the presence of a cosmological constant. In particular, the cosmological term contains the full-fledged curved volume of the 4-simplex. Interestingly, the volume term stems from the asymptotics of the Chern–Simons action. This can be understood as arising from the relation between Chern–Simons theory on the boundary of a region, and a theory defined by an F 2 action in the bulk. Another peculiarity of our approach is that the sign of the curvature of the reconstructed geometry, and hence of the cosmological constant in the Regge action, is not fixed a priori, but rather emerges semiclassically and dynamically from the solution of the equations of motion. In other words, this work suggests a relation between 4-dimensional loop quantum gravity with a cosmological constant and SL ( 2 , C ) Chern–Simons theory in 3 dimensions with knotted graph defects.
118662643
Black Hole Entropy in Loop Quantum Gravity, Analytic Continuation, and Dual Holography
A new approach to black hole thermodynamics is proposed in Loop Quantum Gravity (LQG), by defining a new black hole partition function, followed by analytic continuations of Barbero-Immirzi parameter to $\gamma\in i\mathbb{R}$ and Chern-Simons level to $k\in i\mathbb{R}$. The analytic continued partition function has remarkable features: The black hole entropy $S=A/4\ell_P^2$ is reproduced correctly for infinitely many $\gamma= i\eta$, at least for $\eta\in\mathbb{Z}\setminus\{0\}$. The near-horizon Unruh temperature emerges as the pole of partition function. Interestingly, by analytic continuation the partition function can have a dual statistical interpretation corresponding to a dual quantum theory of $\gamma\in i\mathbb{Z}$. The dual quantum theory implies a semiclassical area spectrum for $\gamma\in i\mathbb{Z}$. It also implies that at a given near horizon (quantum) geometry, the number of quantum states inside horizon is bounded by a holographic degeneracy $d= e^{A/4\ell_P}$, which produces the Bekenstein bound from LQG. On the other hand, the result in arXiv:1212.4060 receives a justification here.
14670965
Dynamics of a scalar field in a polymer-like representation
In the last 20 years, loop quantum gravity, a background-independent approach to unify general relativity and quantum mechanics, has been widely investigated. We consider the quantum dynamics of a real massless scalar field coupled to gravity in this framework. A Hamiltonian operator for the scalar field can be well defined in the coupled diffeomorphism-invariant Hilbert space, which is both self-adjoint and positive. On the other hand, the Hamiltonian constraint operator for the scalar field coupled to gravity can be well defined in the coupled kinematical Hilbert space. There are one-parameter ambiguities due to scalar field in the construction of both operators. The results heighten our confidence that there is no divergence within this background-independent and diffeomorphism-invariant quantization approach of matter coupled to gravity. Moreover, to avoid possible quantum anomaly, the master constraint programme can be carried out in this coupled system by employing a self-adjoint master constraint operator on the diffeomorphism-invariant Hilbert space.