scholarly journals Non-anticommutative quantum gravity

2015 ◽  
Vol 30 (17) ◽  
pp. 1550101 ◽  
Author(s):  
J. W. Moffat
Keyword(s):  
Perturbation Theory ◽  
Quantum Gravity ◽  
Internal Momentum ◽  
Self Energy ◽  
The One ◽  
Gravity Perturbation

A calculation of the one loop gravitational self-energy graph in non-anticommutative quantum gravity reveals that graviton loops are damped by internal momentum dependent factors in the modified propagator and the vertex functions. The non-anticommutative quantum gravity perturbation theory is finite for matter-free gravity and for matter interactions.

scholarly journals Many-Electron QED with Redefined Vacuum Approach

Symmetry ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1014
Author(s):  
Romain N. Soguel ◽  
Andrey V. Volotka ◽  
Dmitry A. Glazov ◽  
Stephan Fritzsche
Keyword(s):  
Perturbation Theory ◽  
Electronic Configuration ◽  
Bound State ◽  
Many Body ◽  
Photon Exchange ◽  
Self Energy ◽  
Many Body Perturbation Theory ◽  
Formula Derivation ◽  
The Many ◽  
The One

The redefined vacuum approach, which is frequently employed in the many-body perturbation theory, proved to be a powerful tool for formula derivation. Here, we elaborate this approach within the bound-state QED perturbation theory. In addition to general formulation, we consider the particular example of a single particle (electron or vacancy) excitation with respect to the redefined vacuum. Starting with simple one-electron QED diagrams, we deduce first- and second-order many-electron contributions: screened self-energy, screened vacuum polarization, one-photon exchange, and two-photon exchange. The redefined vacuum approach provides a straightforward and streamlined derivation and facilitates its application to any electronic configuration. Moreover, based on the gauge invariance of the one-electron diagrams, we can identify various gauge-invariant subsets within derived many-electron QED contributions.

scholarly journals Many-Electron QED with Redefined Vacuum Approach

2021 ◽  
Author(s):  
Romain N. Soguel ◽  
Andrey V. Volotka ◽  
Dmitry A. Glazov ◽  
Stephan Fritzsche
Keyword(s):  
Perturbation Theory ◽  
Electronic Configuration ◽  
Bound State ◽  
Many Body ◽  
Photon Exchange ◽  
Self Energy ◽  
Many Body Perturbation Theory ◽  
Formula Derivation ◽  
The Many ◽  
The One

The redefined vacuum approach, which is frequently employed in the many-body perturbation theory, proved to be a powerful tool for formula derivation. Here, we elaborate this approach within the bound-state QED perturbation theory. In addition to general formulation, we consider the particular example of a single particle (electron or vacancy) excitation with respect to the redefined vacuum. Starting with simple one-electron QED diagrams, we deduce first- and second-order many-electron contributions: screened self-energy, screened vacuum polarization, one-photon exchange, and two-photon exchange. The redefined vacuum approach provides a straightforward and streamlined derivation and facilitates its application to any electronic configuration. Moreover, based on the gauge invariance of the one-electron diagrams, we can identify various gauge-invariant subsets within derived many-electron QED contributions.

scholarly journals The contribution of effective quantum gravity to the high energy scattering in the framework of modified perturbation theory and one loop approximation

2019 ◽  
Vol 79 (10) ◽  
Author(s):  
Nguyen Suan Han ◽  
Do Thu Ha ◽  
Nguyen Nhu Xuan
Keyword(s):  
Perturbation Theory ◽  
Quantum Gravity ◽  
Scattering Amplitude ◽  
High Energy ◽  
Effective Theory ◽  
Potential Equation ◽  
Scalar Particles ◽  
Loop Approximation ◽  
The One ◽  
High Energy Scattering

Abstract The asymptotic behavior of the scattering amplitude for two scalar particles at high energies with fixed momentum transfers is studied. The study is done within the effective theory of quantum gravity based on quasi-potential equation. By using the modified perturbation theory, a systematic method is developed to find the leading eikonal scattering amplitudes together with corrections to them in the one-loop gravitational approximation. The relation is established and discussed between the solutions obtained by means of the operator and functional approaches applied to quasi-potential equation. The first non-leading corrections to the leading eikonal amplitude are found.

scholarly journals Detecting deformed commutators with exceptional points in optomechanical sensors

2021 ◽  
Author(s):  
Dianzhen Cui ◽  
Tao Li ◽  
Jianning Li ◽  
Xuexi Yi
Keyword(s):  
Models Of Quantum Gravity ◽  
Quantum Gravity ◽  
The Other ◽  
Exceptional Point ◽  
Weak Effect ◽  
Third Order ◽  
Exceptional Points ◽  
The One ◽  
Gravity Perturbation ◽  
Canonical Position

Abstract Models of quantum gravity imply a modification of the canonical position-momentum commutation relations. In this manuscript, working with a binary mechanical system, we examine the effect of quantum gravity on the exceptional points of the system. On the one side, we find that the exceedingly weak effect of quantum gravity can be sensed via pushing the system towards a second-order exceptional point, where the spectra of the non-Hermitian system exhibits non-analytic and even discontinuous behavior. On the other side, the gravity perturbation will affect the sensitivity of the system to deposition mass. In order to further enhance the sensitivity of the system to quantum gravity, we extend the system to the other one which has a third-order exceptional point. Our work provides a feasible way to use exceptional points as a new tool to explore the effect of quantum gravity.

scholarly journals Master integrals for bipartite cuts of three-loop photon self energy

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
R. N. Lee ◽  
A. I. Onishchenko
Keyword(s):  
Spectral Density ◽  
High Energy ◽  
Elliptic Integrals ◽  
Iterated Integrals ◽  
Self Energy ◽  
Complete Elliptic Integrals ◽  
The One

Abstract We calculate the master integrals for bipartite cuts of the three-loop propagator QED diagrams. These master integrals determine the spectral density of the photon self energy. Our results are expressed in terms of the iterated integrals, which, apart from the 4m cut (the cut of 4 massive lines), reduce to Goncharov’s polylogarithms. The master integrals for 4m cut have been calculated in our previous paper in terms of the one-fold integrals of harmonic polylogarithms and complete elliptic integrals. We provide the threshold and high-energy asymptotics of the master integrals found, including those for 4m cut.

RENORMALIZATION OF FERMI VELOCITY IN A COMPOSITE TWO DIMENSIONAL ELECTRON GAS

1993 ◽  
Vol 07 (01n03) ◽  
pp. 87-94 ◽  
Author(s):  
M. WEGER ◽  
L. BURLACHKOV
Keyword(s):  
Electron Gas ◽  
Fermi Velocity ◽  
Bohr Radius ◽  
Dimensional Electron ◽  
Temperature Dependent ◽  
Two Dimensional Electron Gas ◽  
Self Energy ◽  
2D System ◽  
Dimensional Electron Gas ◽  
The One

We calculate the self-energy Σ(k, ω) of an electron gas with a Coulomb interaction in a composite 2D system, consisting of metallic layers of thickness d ≳ a 0, where a 0 = ħ2∊1/ me 2 is the Bohr radius, separated by layers with a dielectric constant ∊2 and a lattice constant c perpendicular to the planes. The behavior of the electron gas is determined by the dimensionless parameters k F a 0 and k F c ∊2/∊1. We find that when ∊2/∊1 is large (≈5 or more), the velocity v(k) becomes strongly k-dependent near k F , and v ( k F ) is enhanced by a factor of 5-10. This behavior is similar to the one found by Lindhard in 1954 for an unscreened electron gas; however here we take screening into account. The peak in v(k) is very sharp (δ k/k F is a few percent) and becomes sharper as ∊2/∊1 increases. This velocity renormalization has dramatic effects on the transport properties; the conductivity at low T increases like the square of the velocity renormalization and the resistivity due to elastic scattering becomes temperature dependent, increasing approximately linearly with T. For scattering by phonons, ρ ∝ T 2. Preliminary measurements suggest an increase in v k in YBCO very close to k F .

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