scholarly journals Multi-particle systems in quantum spacetime and a novel challenge for center-of-mass motion

2021 ◽  
Vol 30 (06) ◽  
pp. 2150046
Author(s):  
Giovanni Amelino-Camelia ◽  
Valerio Astuti ◽  
Michelangelo Palmisano ◽  
Michele Ronco
Keyword(s):  
Center Of Mass ◽  
Planck Scale ◽  
Total Momentum ◽  
Particle Systems ◽  
Mass Motion ◽  
Multiparticle System ◽  
Standard Linear ◽  
Noncommutative Spacetime ◽  
Multiparticle Systems ◽  
Quantum Spacetime

In recent times, there has been considerable interest in scenarios for quantum gravity in which particle kinematics is affected nonlinearly by the Planck scale, with encouraging results for the phenomenological prospects, but also some concerns that the nonlinearities might produce pathological properties for composite/multiparticle systems. We here focus on kinematics in the [Formula: see text]-Minkowski noncommutative spacetime, the quantum spacetime which has been most studied from this perspective and compare the implications of the alternative descriptions of the total momentum of a multiparticle system which have been so far proposed. We provide evidence suggesting that priority should be given to defining the total momentum as the standard linear sum of the momenta of the particles composing the system. We also uncover a previously unnoticed feature concerning some (minute but conceptually important) effects on center-of-mass motion due to properties of the motion of the constituents relative to the center of mass.

Center-of-Mass Motion in Many-Particle Systems

1957 ◽  
Vol 108 (2) ◽  
pp. 482-490 ◽  
Author(s):  
S. Gartenhaus ◽  
C. Schwartz
Keyword(s):  
Center Of Mass ◽  
Particle Systems ◽  
Mass Motion

Center-of-Mass Motion in Many-Particle Systems

1973 ◽  
Vol 7 (3) ◽  
pp. 925-930 ◽  
Author(s):  
D. J. Ernst ◽  
C. M. Shakin ◽  
R. M. Thaler
Keyword(s):  
Center Of Mass ◽  
Particle Systems ◽  
Mass Motion

Center-of-Mass Motion in Many-Particle Systems. II. Critique of the Gartenhaus-Schwartz Transformation

1973 ◽  
Vol 7 (4) ◽  
pp. 1340-1343 ◽  
Author(s):  
D. J. Ernst ◽  
C. M. Shakin ◽  
R. M. Thaler
Keyword(s):  
Center Of Mass ◽  
Particle Systems ◽  
Mass Motion

scholarly journals Infrared effects in the late stages of black hole evaporation

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Éanna É. Flanagan
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Center Of Mass ◽  
Planck Scale ◽  
Black Hole Mass ◽  
Order Unity ◽  
Intrinsic Angular Momentum ◽  
Hole Position ◽  
Late Stages ◽  
Shear Tensor

Abstract As a black hole evaporates, each outgoing Hawking quantum carries away some of the black holes asymptotic charges associated with the extended Bondi-Metzner-Sachs group. These include the Poincaré charges of energy, linear momentum, intrinsic angular momentum, and orbital angular momentum or center-of-mass charge, as well as extensions of these quantities associated with supertranslations and super-Lorentz transformations, namely supermomentum, superspin and super center-of-mass charges (also known as soft hair). Since each emitted quantum has fluctuations that are of order unity, fluctuations in the black hole’s charges grow over the course of the evaporation. We estimate the scale of these fluctuations using a simple model. The results are, in Planck units: (i) The black hole position has a uncertainty of $$ \sim {M}_i^2 $$ ∼ M i 2 at late times, where Mi is the initial mass (previously found by Page). (ii) The black hole mass M has an uncertainty of order the mass M itself at the epoch when M ∼ $$ {M}_i^{2/3} $$ M i 2 / 3 , well before the Planck scale is reached. Correspondingly, the time at which the evaporation ends has an uncertainty of order $$ \sim {M}_i^2 $$ ∼ M i 2 . (iii) The supermomentum and superspin charges are not independent but are determined from the Poincaré charges and the super center-of-mass charges. (iv) The supertranslation that characterizes the super center-of-mass charges has fluctuations at multipole orders l of order unity that are of order unity in Planck units. At large l, there is a power law spectrum of fluctuations that extends up to l ∼ $$ {M}_i^2/M $$ M i 2 / M , beyond which the fluctuations fall off exponentially, with corresponding total rms shear tensor fluctuations ∼ MiM−3/2.

NUCLEON IN NUCLEAR MEDIUM

2009 ◽  
Vol 18 (05n06) ◽  
pp. 1166-1175
Author(s):  
SHASHIKANT C. PHATAK
Keyword(s):  
Standard Procedure ◽  
Center Of Mass ◽  
Critical Density ◽  
Magnetic Interaction ◽  
Nuclear Medium ◽  
Mass Motion ◽  
Field Equations ◽  
Dielectric Model ◽  
Chiral Color Dielectric Model

The behavior of a nucleon in nuclear medium is discussed in Chiral Color Dielectric Model. It is assumed that the nucleons in nuclear medium produces a background dielectric field and the quark and dielectric field equations are solved self consistantly in presence of the dielectric field. A nucleon in nuclear medium is then constructed by means of standard procedure followed in chiral bag models. The corrections due to center of mass motion, color magnetic interaction and meson interaction are included. The calculations show that the nucleon becomes bigger in the medium but its mass does not change much. It is found that beyond a certian density, bound solutions in which quarks are bound in self-generated dielectric field are not possible. Thus, the calculations indicate that there is a critical density beyond which the matter consists of deconfined quarks.

scholarly journals PROPOSAL OF A SECOND GENERATION OF QUANTUM-GRAVITY-MOTIVATED LORENTZ-SYMMETRY TESTS: SENSITIVITY TO EFFECTS SUPPRESSED QUADRATICALLY BY THE PLANCK SCALE

2003 ◽  
Vol 12 (09) ◽  
pp. 1633-1639 ◽  
Author(s):  
GIOVANNI AMELINO-CAMELIA
Keyword(s):  
Quantum Gravity ◽  
Second Generation ◽  
Loop Quantum Gravity ◽  
Planck Scale ◽  
Cosmic Ray ◽  
Lorentz Symmetry ◽  
Planck Length ◽  
Satisfactory Description ◽  
Symmetry Tests ◽  
Quantum Spacetime

Over the last few years the study of possible Planck-scale departures from classical Lorentz symmetry has been one of the most active areas of quantum-gravity research. We now have a satisfactory description of the fate of Lorentz symmetry in the most popular noncommutative spacetimes and several studies have been devoted to the fate of Lorentz symmetry in loop quantum gravity. Remarkably there are planned experiments with enough sensitivity to reveal these quantum-spacetime effects, if their magnitude is only linearly suppressed by the Planck length. Unfortunately, in some quantum-gravity scenarios even the strongest quantum-spacetime effects are suppressed by at least two powers of the Planck length, and many authors have argued that it would be impossible to test these quadratically-suppressed effects. I here observe that advanced cosmic-ray observatories and neutrino observatories can provide the first elements of an experimental programme testing the possibility of departures from Lorentz symmetry that are quadratically Planck-length suppressed.

Spontaneous emission in a standing-wave cavity: Classical center-of-mass motion

1992 ◽  
Vol 46 (11) ◽  
pp. 7162-7178 ◽  
Author(s):  
W. Ren ◽  
J. D. Cresser ◽  
H. J. Carmichael
Keyword(s):  
Standing Wave ◽  
Spontaneous Emission ◽  
Center Of Mass ◽  
Mass Motion
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