Transversality of the resummed thermal gluon self-energy

1993 ◽  
Vol 71 (5-6) ◽  
pp. 256-261 ◽  
Author(s):  
G. Kunstatter
Keyword(s):  
Quantum Chromodynamics ◽  
Imaginary Part ◽  
The Self ◽  
Ward Identities ◽  
Generating Functional ◽  
The Real ◽  
Self Energy ◽  
Gauge Fixing

The perturbative Ward identities obeyed by the effective vertices and propagators for thermal quantum chromodynamics (QCD) have recently been used to prove to order g2T the on-shell transversality of the imaginary part of the (resummed) gluon self-energy in all linear gauges. Here the same result is derived for both the real and imaginary parts of the self-energy using the nonperturbative gauge-fixing identities obeyed by the generating functional for QCD.

scholarly journals Opacity from Loops in AdS

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Alexandria Costantino ◽  
Sylvain Fichet
Keyword(s):  
Imaginary Part ◽  
Quantum Dynamics ◽  
Model Building ◽  
Asymptotic Properties ◽  
The Self ◽  
Effective Theory ◽  
Self Energy ◽  
Higher Dimensional ◽  
Timelike Region ◽  
Spectral Representations

Abstract We investigate how quantum dynamics affects the propagation of a scalar field in Lorentzian AdS. We work in momentum space, in which the propagator admits two spectral representations (denoted “conformal” and “momentum”) in addition to a closed-form one, and all have a simple split structure. Focusing on scalar bubbles, we compute the imaginary part of the self-energy ImΠ in the three representations, which involves the evaluation of seemingly very different objects. We explicitly prove their equivalence in any dimension, and derive some elementary and asymptotic properties of ImΠ.Using a WKB-like approach in the timelike region, we evaluate the propagator dressed with the imaginary part of the self-energy. We find that the dressing from loops exponentially dampens the propagator when one of the endpoints is in the IR region, rendering this region opaque to propagation. This suppression may have implications for field-theoretical model-building in AdS. We argue that in the effective theory (EFT) paradigm, opacity of the IR region induced by higher dimensional operators censors the region of EFT breakdown. This confirms earlier expectations from the literature. Specializing to AdS5, we determine a universal contribution to opacity from gravity.

scholarly journals Self-Consistent Calculation of Particle-Hole Diagrams on the Matsubara Frequency: Flex Approximation

1997 ◽  
Vol 08 (05) ◽  
pp. 1145-1158
Author(s):  
J. J. Rodríguez-Núñez ◽  
S. Schafroth
Keyword(s):  
Hubbard Model ◽  
Imaginary Part ◽  
Chemical Potential ◽  
Order Approximation ◽  
The Self ◽  
Green Functions ◽  
Matsubara Frequency ◽  
Self Energy ◽  
Peak Structure ◽  
Self Consistent

We implement the numerical method of summing Green function diagrams on the Matsubara frequency axis for the fluctuation exchange (FLEX) approximation. Our method has previously been applied to the attractive Hubbard model for low density. Here we apply our numerical algorithm to the Hubbard model close to half filling (ρ =0.40), and for T/t = 0.03, in order to study the dynamics of one- and two-particle Green functions. For the values of the chosen parameters we see the formation of three branches which we associate with the two-peak structure in the imaginary part of the self-energy. From the imaginary part of the self-energy we conclude that our system is a Fermi liquid (for the temperature investigated here), since Im Σ( k , ω) ≈ w2 around the chemical potential. We have compared our fully self-consistent FLEX solutions with a lower order approximation where the internal Green functions are approximated by free Green functions. These two approches, i.e., the fully self-consistent and the non-self-consistent ones give different results for the parameters considered here. However, they have similar global results for small densities.

Spin radiation effects in the BMT model of spinning charge

2014 ◽  
Vol 29 (31) ◽  
pp. 1450186 ◽  
Author(s):  
S. L. Lebedev
Keyword(s):  
Imaginary Part ◽  
Radiation Effects ◽  
Degrees Of Freedom ◽  
The Self ◽  
Spin Magnetic Moment ◽  
Self Energy ◽  
Radiation Processes ◽  
Nonzero Spin ◽  
Derivatives Of ◽  
Spin Contribution

The radiation processes emerging as a result of interaction between spin and orbit degrees of freedom of spinning charge are investigated with the use of the Bargmann–Michel–Telegdi (BMT) model. The spin contribution to the self-energy of the ultrarelativistic particle is imaginary and proportional to invariant constructed from the derivatives of the worldline and from the spin. This invariant determines up to negative numerical factor of the QED spin contribution to the imaginary part of the mass shift (MS). Particular cases of crossed, electric and magnetic external fields are considered in detail. The influence of an ideal boundary upon the self-energy of the particle is analyzed for the crossed field case. In the presence of the "mirror" the imaginary part of the MS gets an addition and the nonzero spin dependent real part appears, both however giving the small corrections to no-boundary MS. An alternative method to obtain the spin magnetic moment correction to the power of synchrotron radiation entails in generalization of the result known for the planar motion. Special attention is given to disagreement between classical and quantum pictures of spin radiation.

scholarly journals Finite calculation of divergent self-energy diagrams

2003 ◽  
Vol 81 (12) ◽  
pp. 1433-1445 ◽  
Author(s):  
A Aste ◽  
D Trautmann
Keyword(s):  
Perturbation Theory ◽  
Dispersion Relation ◽  
Imaginary Part ◽  
Feynman Diagram ◽  
Feynman Diagrams ◽  
Energy Diagram ◽  
The Real ◽  
Self Energy ◽  
Single Integral ◽  
Analytic Expression

Using dispersive techniques, it is possible to avoid ultraviolet divergences in the calculation of Feynman diagrams, making subsequent regularization of divergent diagrams unnecessary. We give a simple introduction to the most important features of such dispersive techniques in the framework of the so-called finite causal perturbation theory. The method is also applied to the "divergent" general massive two-loop sunrise self-energy diagram, where it leads directly to an analytic expression for the imaginary part of the diagram in accordance with the literature, whereas the real part can be obtained by a single integral dispersion relation. It is pointed out that dispersive methods have been known for decades and have been applied to several nontrivial Feynman diagram calculations.PACS Nos.: 11.10.–z, 11.15.Bt, 12.20.Ds, 12.38.Bx

Gauge-fixing dependence of gluon and quark-damping rates in hot quantum chromodynamics

1993 ◽  
Vol 71 (5-6) ◽  
pp. 208-214 ◽  
Author(s):  
R. Baier ◽  
G. Kunstatter ◽  
D. Schiff
Keyword(s):  
Quantum Chromodynamics ◽  
High Temperatures ◽  
Ward Identities ◽  
Gauge Fixing ◽  
Hard Thermal Loops

The recently observed gauge-fixing dependence in covariant gauges of the damping rates of the quantum chromodynamics (QCD) gluonic and fermionic excitations at high temperatures and long wavelengths is reviewed. The analysis is based on the method by Braaten and Pisarski for resumming hard thermal loops using the Ward identities satisfied by the effective propagators and vertex functions. A proposed resolution of the gauge problem by regularizing the mass singularities is also discussed.

Comparison of the self-expanding Evolut-PRO transcatheter aortic valve to its predecessor Evolut-R in the real world multicenter ATLAS registry

2020 ◽  
Vol 310 ◽  
pp. 120-125
Author(s):  
Konstantinos Kalogeras ◽  
Neil Ruparelia ◽  
Tito Kabir ◽  
Richard Jabbour ◽  
Toru Naganuma ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Real World ◽  
The Self ◽  
The Real ◽  
Transcatheter Aortic Valve

scholarly journals Classical gravitational self-energy from double copy

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Gabriel Luz Almeida ◽  
Stefano Foffa ◽  
Riccardo Sturani
Keyword(s):  
Gravitational Field ◽  
Binary System ◽  
The Self ◽  
Gravitational Coupling ◽  
Leading Order ◽  
Body System ◽  
Self Energy ◽  
Composite Systems ◽  
Body Dynamics ◽  
Double Copy

Abstract We apply the classical double copy to the calculation of self-energy of composite systems with multipolar coupling to gravitational field, obtaining next-to-leading order results in the gravitational coupling GN by generalizing color to kinematics replacement rules known in literature. When applied to the multipolar description of the two-body system, the self-energy diagrams studied in this work correspond to tail processes, whose physical interpretation is of radiation being emitted by the non-relativistic source, scattered by the curvature generated by the binary system and then re-absorbed by the same source. These processes contribute to the conservative two-body dynamics and the present work represents a decisive step towards the systematic use of double copy within the multipolar post-Minkowskian expansion.

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