scholarly journals EXTENSION OF THE SHIRAFUJI MODEL FOR MASSIVE PARTICLES WITH SPIN

2006 ◽  
Vol 21 (19n20) ◽  
pp. 4137-4160 ◽  
Author(s):  
SERGEY FEDORUK ◽  
ANDRZEJ FRYDRYSZAK ◽  
JERZY LUKIERSKI ◽  
CÈSAR MIQUEL-ESPANYA
Keyword(s):  
Electric Charge ◽  
Degrees Of Freedom ◽  
Twistor Space ◽  
Space Time ◽  
Particle Model ◽  
Intermediate Step ◽  
Time Coordinate ◽  
Massive Particles ◽  
Relativistic Particles ◽  
Primary Space

We extend the Shirafuji model for massless particles with primary space–time coordinates and composite four-momenta to a model for massive particles with spin and electric charge. The primary variables in the model are the space–time four-vector, four scalars describing spin and charge degrees of freedom as well as a pair of Weyl spinors. The geometric description proposed in this paper provides an intermediate step between the free purely twistorial model in two-twistor space in which both space–time and four-momenta vectors are composite, and the standard particle model, where both space–time and four-momenta vectors are elementary. We quantize the model and find explicitly the first-quantized wave functions describing relativistic particles with mass, spin and electric charge. The space–time coordinates in the model are not commutative; this leads to a wave function that depends only on one covariant projection of the space–time four-vector (covariantized time coordinate) defining plane wave solutions.

scholarly journals Group Contractions: Inonu, Wigner, and Einstein

1997 ◽  
Vol 12 (01) ◽  
pp. 71-78 ◽  
Author(s):  
Y.S. Kim
Keyword(s):  
Degrees Of Freedom ◽  
Small Mass ◽  
Space Time ◽  
Internal Space ◽  
Large Momentum ◽  
Energy Relation ◽  
Large Radius ◽  
Massless Particles ◽  
Massive Particles

Einstein's E = mc2 unifies the momentum-energy relation for massive and massless particles. According to Wigner, the internal space–time symmetries of massive and massless particles are isomorphic to O(3) and E(2) respectively. According to Inonu and Wigner, O(3) can be contracted to E(2) in the large-radius limit. It is noted that the O(3)-like little group for massive particles can be contracted to the E(2)-like little group for massless particles in the limit of large momentum and/or small mass. It is thus shown that transverse rotational degress of freedom for massive particles become contracted to gauge degrees of freedom for massless particles.

scholarly journals LIVING IN CURVED MOMENTUM SPACE

2013 ◽  
Vol 28 (12) ◽  
pp. 1330014 ◽  
Author(s):  
JERZY KOWALSKI-GLIKMAN
Keyword(s):  
Quantum Gravity ◽  
Momentum Space ◽  
Degrees Of Freedom ◽  
Space Time ◽  
Topological Phase ◽  
De Sitter ◽  
Interacting Particles ◽  
Detailed Review ◽  
Theory Of Gravity ◽  
Relativistic Particles

In this paper, we review some aspects of relativistic particles' mechanics in the case of a nontrivial geometry of momentum space. We start by showing how the curved momentum space arises in the theory of gravity in 2+1 dimensions coupled to particles, when (topological) degrees of freedom of gravity are solved for. We argue that there might exist a similar topological phase of quantum gravity in 3+1 dimensions. Then, we characterize the main properties of the theory of interacting particles with curved momentum space and the symmetries of the action. We discuss the space–time picture and the emergence of the principle of relative locality, according to which locality of events is not absolute but becomes observer dependent, in the controllable, relativistic way. We conclude with the detailed review of the most studied κ-Poincaré framework, which corresponds to the de Sitter momentum space.

CRYSTALLINE GRAVITY

2009 ◽  
Vol 24 (18n19) ◽  
pp. 3243-3255 ◽  
Author(s):  
GERARD 't HOOFT
Keyword(s):  
Finite Number ◽  
Lorentz Group ◽  
Degrees Of Freedom ◽  
Holonomy Group ◽  
Discrete Subgroup ◽  
Analytic Solutions ◽  
Space Time ◽  
Exact Analytic Solutions ◽  
Finite Domains ◽  
Dimensional Crystal

Matter interacting classically with gravity in 3+1 dimensions usually gives rise to a continuum of degrees of freedom, so that, in any attempt to quantize the theory, ultraviolet divergences are nearly inevitable. Here, we investigate a theory that only displays a finite number of degrees of freedom in compact sections of space-time. In finite domains, one has only exact, analytic solutions. This is achieved by limiting ourselves to straight pieces of string, surrounded by locally flat sections of space-time. Next, we suggest replacing in the string holonomy group, the Lorentz group by a discrete subgroup, which turns space-time into a 4-dimensional crystal with defects.

scholarly journals BLACK HOLE EVAPORATION BASED UPON A q-DEFORMATION DESCRIPTION

2005 ◽  
Vol 20 (26) ◽  
pp. 6039-6049 ◽  
Author(s):  
XIN ZHANG
Keyword(s):  
Black Hole ◽  
Degrees Of Freedom ◽  
Radiation Spectrum ◽  
Correlation Effect ◽  
Space Time ◽  
Noncommutative Space ◽  
Schwarzschild Black Hole ◽  
Black Hole Evaporation ◽  
Starting Point ◽  
New Distribution

A toy model based upon the q-deformation description for studying the radiation spectrum of black hole is proposed. The starting point is to make an attempt to consider the space–time noncommutativity in the vicinity of black hole horizon. We use a trick that all the space–time noncommutative effects are ascribed to the modification of the behavior of the radiation field of black hole and a kind of q-deformed degrees of freedom are postulated to mimic the radiation particles that live on the noncommutative space–time, meanwhile the background metric is preserved as usual. We calculate the radiation spectrum of Schwarzschild black hole in this framework. The new distribution deviates from the standard thermal spectrum evidently. The result indicates that some correlation effect will be introduced to the system if the noncommutativity is taken into account. In addition, an infrared cutoff of the spectrum is the prediction of the model.

An accurate method to include lubrication forces in numerical simulations of dense Stokesian suspensions

2015 ◽  
Vol 769 ◽  
pp. 369-386 ◽  
Author(s):  
A. Lefebvre-Lepot ◽  
B. Merlet ◽  
T. N. Nguyen
Keyword(s):  
Short Range ◽  
Degrees Of Freedom ◽  
Computational Cost ◽  
Parameter Tuning ◽  
Accurate Method ◽  
Spherical Particles ◽  
Particle Model ◽  
Stokesian Dynamics ◽  
New Feature ◽  
The Many

We address the problem of computing the hydrodynamic forces and torques among $N$ solid spherical particles moving with given rotational and translational velocities in Stokes flow. We consider the original fluid–particle model without introducing new hypotheses or models. Our method includes the singular lubrication interactions which may occur when some particles come close to one another. The main new feature is that short-range interactions are propagated to the whole flow, including accurately the many-body lubrication interactions. The method builds on a pre-existing fluid solver and is flexible with respect to the choice of this solver. The error is the error generated by the fluid solver when computing non-singular flows (i.e. with negligible short-range interactions). Therefore, only a small number of degrees of freedom are required and we obtain very accurate simulations within a reasonable computational cost. Our method is closely related to a method proposed by Sangani & Mo (Phys. Fluids, vol. 6, 1994, pp. 1653–1662) but, in contrast with the latter, it does not require parameter tuning. We compare our method with the Stokesian dynamics of Durlofsky et al. (J. Fluid Mech., vol. 180, 1987, pp. 21–49) and show the higher accuracy of the former (both by analysis and by numerical experiments).

NEW MANIFESTLY COVARIANT MODELS FOR RELATIVISTIC PARTICLES OF ARBITRARY SPIN

1991 ◽  
Vol 06 (05) ◽  
pp. 807-844 ◽  
Author(s):  
ROBERT MARNELIUS ◽  
ULF MÅRTENSSON
Keyword(s):  
Arbitrary Spin ◽  
Internal Variables ◽  
Spinning Particles ◽  
Massive Particles ◽  
Relativistic Particles

By means of a previously developed procedure for the derivation of manifestly Lorentz covariant models of spinning particles, we derive new classes of models in which the internal variables transform as Lorentz spinors. Models for massless and massive particles of arbitrary spin are given in which the internal variables are fermionic or bosonic spinors. Lagrangians and their local invariances are explicitly written down for all models.

Spinning strings of the Neveu-Schwarz-Ramond type in 3, 4, 6, and 10 space-time dimensions

1999 ◽  
Vol 77 (6) ◽  
pp. 427-446
Author(s):  
S B Phillips
Keyword(s):  
Degrees Of Freedom ◽  
Lagrangian Density ◽  
Dimensional Space ◽  
Equations Of Motion ◽  
Physical Space ◽  
Space Time ◽  
Coordinate Space ◽  
Time Dimension ◽  
Light Cone Gauge ◽  
Fermionic Sector

A model of a spinning string with an internal coordinate index is proposed and studied. When the action for this model is taken to be diagonal in this internal coordinate space and quantized in the light-cone gauge it is found to be Lorentz covariant in four-dimensional space-time provided that the internal coordinate space is four dimensional.This combination of space-time dimension, D, and internal coordinate space dimension, N, is just one of four possible sets, the other three corresponding to D = 3, 6, and 10, precisely the same values for which it is possible to formulate Yang-Mills theories with simple supersymmetry. By comparing the number of propagating degrees of freedom at the zero-mass level in the open string bosonic and fermionic sectors it is found that a supersymmetric interpretation of this model is possible provided that all physical states in the bosonic sector have even G-parity and the ground-state spin or in the fermionic sector have positive chirality. A possible interpretation of the connection betweenthe N components of each of the D space-time coordinates is presentedon the basis that the space-time coordinates are scalars in the internal coordinate space. This interpretation would appear to be reasonable given the fact that the field variables in the Lagrangian density do not necessarily have to represent physically measurable quantities but can, instead, only represent physically measurable quantities when combined in some manner, the simplest of which being a linear combination. The Lagrangian density simply produces the equations of motion and the constraint equations for the independent variables, only linear combinations of which represent the four dimensions of physical space-time.PACS Nos.: 11.17.+y, 11.10.Qr, 1.30.Cp, 11.30.Pb

scholarly journals Gravitational Theory Without the Cosmological Constant Problem

1997 ◽  
Vol 12 (32) ◽  
pp. 2421-2424 ◽  
Author(s):  
E. I. Guendelman ◽  
A. B. Kaganovich
Keyword(s):  
Cosmological Constant ◽  
Degrees Of Freedom ◽  
Vacuum Energy ◽  
Dimensional Space ◽  
Realistic Model ◽  
Gravitational Theory ◽  
Space Time ◽  
Higher Dimensional Space Time ◽  
Higher Dimensional ◽  
Dimensional Space Time

We develop a gravitational theory where the measure of integration in the action principle is not necessarily [Formula: see text] but it is determined dynamically through additional degrees of freedom. This theory is based on the demand that such measure respects the principle of "non-gravitating vacuum energy" which states that the Lagrangian density L can be changed to L + const. without affecting the dynamics. Formulating the theory in the first-order formalism we get as a consequence of the variational principle a constraint that enforces the vanishing of the cosmological constant. The most realistic model that implements these ideas is realized in a six or higher dimensional space–time. The compactification of extra dimensions into a sphere gives the possibility of generating scalar masses and potentials, gauge fields and fermionic masses. It turns out that the remaining four-dimensional space–time must have effective zero cosmological constant.

Space‐time geometry of relativistic particles

1990 ◽  
Vol 31 (1) ◽  
pp. 55-60 ◽  
Author(s):  
Y. S. Kim ◽  
E. P. Wigner
Keyword(s):  
Space Time ◽  
Relativistic Particles
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