Yakov Itin
A covariant gauge independent derivation of the generalized dispersion relation of electromagnetic waves in a medium with local and linear constitutive law is presented. A generalized photon propagator is derived. For Maxwell constitutive tensor, the standard light cone structure and the standard Feynman propagator are reinstated.
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In the framework of the operator product expansion I provide a detailed evaluation of the contribution of the lowest photon condensate to the two-point photon Green function for four-dimensional spinor electrodynamics and three-dimensional scalar electrodynamics. Since the above mentioned condensate affects the part of the propagator contributing to physical amplitudes I suggest that this condensate could play a role in the non-perturbative dynamics of Abelian gauge field theories.
Electrodynamics with a local and linear constitutive law is used as a framework for models violating Lorentz covariance. The constitutive tensor of such a construction is irreducibly decomposed into three independent pieces. The principal part is the anisotropic generalisation of the standard electrodynamics. The two other parts, axion and skewon, represent non-classical modifications of electrodynamics. We derive the expression for the photon propagator in the Minkowski spacetime endowed with a skewon field. For a relatively small (antisymmetric) skewon field, a modified Coulom law is exhibit…
Two different systems of the generalized coherent states for the de Sitter group are constructed. These systems have the physical sense of particles and antiparticles over de Sitter space and obeys the Klein-Gordon equation. Using these systems the de Sitter-invariant propagators for massive spin~0 and~1/2 fields over de Sitter space are constructed.
We construct a de Sitter invariant photon propagator in general covariant gauges. Our result is a natural generalization of the Allen-Jacobson photon propagator in Feynman gauge. Our propagator reproduces the correct response to a point static charge and the one-loop electromagnetic stress-energy tensor, strongly suggesting that it is suitable for perturbative calculations on de Sitter.
We derive the photon propagator in light-shell gauge, which was first introduced in the context of light-shell effective theory.
The axion modified electrodynamics is usually used as a model for description of possible violation of Lorentz invariance in field theory. The low-energy manifestation of Lorentz violation can hopefully be observed in experiments with the electromagnetic waves. It justifies the importance of study how a small axion addition can modify the wave propagation. Although a constant axion does not contribute to the dispersion relation at all, even a slowly varying axion field destroys the light cone structure. In this paper, we study the wave propagation in the axion modified electrodynamics in the f…
We explore a connection between generalized uncertainty principle (GUP) and modified Hořava-Lifshitz (HL) gravity. The GUP density function may be replaced by the cutoff function for the renormalization group of modified Hořava-Lifshitz gravity. We find the GUP-corrected graviton propagators and compare these with tensor propagators in the HL gravity. Two are qualitatively similar, but the $p^5$-term arisen from Cotton tensor is missed in the GUP-corrected graviton propagator.
In principle, calculation of a full Green's function in any field theory requires knowledge of the infinite set of multi-point Green's functions, unless one can find some way of truncating the corresponding Schwinger-Dyson equations. For the fermion and boson propagators in QED this requires an {\it ansatz} for the full three point vertex. Here we illustrate how the properties of gauge invariance, gauge covariance and multiplicative renormalizability impose severe constraints on this fermion-boson interaction, allowing a consistent truncation of the propagator equations. We demonstrate how the…
We calculate and discuss the one-loop corrections to the photon sector of QED interacting to a background gravitational field. At high energies the fermion field can be taken as massless and the quantum terms can be obtained by integrating conformal anomaly. We present a covariant local expression for the corresponding effective action, similar to the one obtained earlier for the gravitational sector. At the moderate energies the quantum terms can be obtained through the heat kernel method. In this way we derive the exact one-loop beta-function for the electric charge in the momentum subtracti…
We consider properties of connected diagrams with fermion-photon interaction and such fermion and photon propagators and vertex function that the values of these diagrams are finite. We establish the properties of these propagators and vertex function that imply that these diagrams are invariant under C, P, T, CP, CT, PT, or CPT transformations up to some phase factor common to each process. We introduce eight new transformations related to Hermiticity and establish the conditions under which they leave the tree transition probabilities invariant. We determine such general Lorentz form-invaria…
Bulk-to-bulk photon propagator in AdS
研究AdS中不同规范下光子体到体传播子的构造，通过动量与位置空间技术确保规范不变性，并得到轴向、库仑和协变规范下的新表达式。
The non-perturbative structure of the photon and gluon propagators plays an important role in governing the dynamics of quantum electrodynamics (QED) and quantum chromodynamics (QCD) respectively. Although it is often assumed that these interacting field propagators can be decomposed into longitudinal and transverse components, as for the free case, it turns out that in general this is not possible. Moreover, the non-abelian gauge symmetry of QCD permits the momentum space gluon propagator to contain additional singular terms involving derivatives of $δ(p)$, the appearance of which is related …
We construct explicit integral relations between propagators of generalized Schrödinger equations that are linked by higher-order supersymmetry. Our results complement and extend the findings obtained in J. Phys.A 40, 10557 (2007) for the conventional Schrödinger equation.
We study the behavior of the fermion propagator in an external time dependent potential in 0+1 dimension. We show that, when the potential has upto quadratic terms in time, the propagator can be expressed in terms of generalized Airy functions (or standard Airy functions depending on the exact time dependence). We study various properties of these new generalized functions which reduce to the standard Airy functions in a particular limit.
Photon propagator in de Sitter space in the general covariant gauge
本文在一般协变规范下，采用正则量子化方法构造了 $D$ 维 de Sitter 时空中的光子传播子，并证明其位置空间传播子必然破坏 de Sitter 对称性（精确横向规范极限除外）。
Even the photon propagator must break de Sitter symmetry
本文指出德西特空间中无质量矢量场传播子因必须满足此前被忽视的Ward-Takahashi恒等式而无法保持德西特不变性，构造了满足一致量子化条件的传播子，并指出该解虽属线性理论规范部分，但在包含相互作用时必须予以考虑。
Photon propagator for inflation in the general covariant gauge
在正则量子化框架内，于一般协变规范下研究幂律暴胀的光子传播子，显式构造了简单协变规范下的位置空间传播子，并验证了其极限与可观测量计算的一致性。
We discuss the influence of closed Dirac strings on the photon propagator in the Landau gauge emerging from a study of the compact U(1) gauge model in 2+1 dimensions. This gauge also minimizes the total length of the Dirac strings. Closed Dirac strings are stable against local gauge-fixing algorithms only due to the torus boundary conditions of the lattice. We demonstrate that these left-over Dirac strings are responsible for the previously observed unphysical behavior of the propagator of space-like photons (D_T) in the deconfinement (high temperature) phase. We show how one can monitor the n…
Applying the principle of analytic extension for generalized functions we derive causal propagators for algebraic non-covariant gauges. The so generated manifestly causal gluon propagator in the light-cone gauge is used to evaluate two one-loop Feynman integrals which appear in the computation of the three-gluon vertex correction. The result is in agreement with that obtained through the usual prescriptions.
We discuss an inherent Pauli-Villars regularization in Bopp-Podolsky's generalized electrodynamics. Introducing gauge-fixing terms for Bopp-Podolsky's generalized electrodynamic action, we realize a unique feature for the corresponding photon propagator with a built-in Pauli-Villars regularization independent of the gauge choice made in Maxwell's usual electromagnetism. According to our realization, the length dimensional parameter $a$ associated with Bopp-Podolsky's higher order derivatives corresponds to the inverse of the Pauli-Villars regularization mass scale $Λ$, i.e. $a = 1/Λ$. Solving …
A system of generalized coherent states for the de Sitter group obeying the Klein-Gordon equation and corresponding to the massive spin zero particles over the de Sitter space is considered. This allows us to construct the quantized scalar field by the resolution over these coherent states; the corresponding propagator is computed by the method of analytic continuation to the complex de Sitter space and coincides with expressions obtained previously by other methods. Considering the case of spin 1/2 we establish the connection of the invariant Dirac equation over the de Sitter space with irred…
In this paper we present an iterative method to generate an infinite class of new nonlocal field theories whose propagators are ghost-free. We first examine the scalar field case and show that the pole structure of such generalized propagators possesses the standard two derivative pole and in addition can contain complex conjugate poles which, however, do not spoil at least tree level unitarity as the optical theorem is still satisfied. Subsequently, we define analogous propagators for the fermionic sector which is also devoid of unhealthy degrees of freedom. As a third case, we apply the same…
Photon Quantization and Propagator in Rotating Coordinates
该论文在刚性旋转圆柱参考系中构建了量子化电磁场及光子传播子，通过协变麦克斯韦理论和贝塞尔函数求解模式，验证了两种构建方法满足格林函数方程，为旋转系中的协变微扰计算提供了基础。
We investigate a close connection between generalized uncertainty principle (GUP) and deformed Hořava-Lifshitz (HL) gravity. The GUP commutation relations correspond to the UV-quantum theory, while the canonical commutation relations represent the IR-quantum theory. Inspired by this UV/IR quantum mechanics, we obtain the GUP-corrected graviton propagator by introducing UV-momentum $p_i=p_{0i}(1+βp_{0}^2)$ and compare this with tensor propagators in the HL gravity. Two are the same up to $p_0^4$-order.
We study the Landau gauge photon propagator in the three--dimensional Abelian Higgs model with compact gauge field and fundamentally charged matter in the London limit. The total gauge field is split into singular and regular parts. On the confinement side of the string breaking crossover the momentum dependence of the total propagator is characterized by an anomalous dimension similarly to 3D compact QED. At the crossover and throughout the Higgs region the anomalous dimension disappears. This result perfectly agrees with recent observations that the monopole--antimonopole plasma leads to non…
The true variables in QED are the transverse photon components and Dirac's physical electron, constructed out of the fermionic field and the longitudinal components of the photon. We calculate the propagators in terms of these variables to one loop and demonstrate their gauge invariance. The physical electron propagator is shown not to suffer from infrared divergences in any gauge. In general, all physical Green's functions are gauge invariant and infrared-finite.
A system of generalized coherent states for the de Sitter group obeying Klein-Gordon equation and corresponding to the massive spin zero particles over the de Sitter space is considered. This allows us to construct the quantized scalar field by the resolution over these coherent states; the corresponding propagator can be computed by the method of analytic continuation to the complexified de Sitter space and coincides with expressions obtained previously by other methods. We show that this propagator possess the de Sitter-invariance and causality properties.
The theory of massive photons in the presence of axions is studied as the effective theory describing the electromagnetic response of semimetals when a particular quartic fermionic pairing perturbation triggers the formation of charged chiral condensates, giving rise to an axionic superconductor. We investigate corrections to the Yukawa-like potential mediated by massive photons due to axion excitations up to one-loop order and compute the modifications of the London penetration length.
Two simple photon gauges in inflation
在任意维度幂律暴胀中，通过两族单参数非协变规范构造了形式更简单的光子传播子，使涉及无质量矢量场的维度正规化圈计算变得可行。
The worldline formalism has previously been used for deriving compact master formulas for the one-loop N-photon amplitudes in both scalar and spinor QED, and in the vacuum as well as in a constant external field. For scalar QED, there is also an analogous master formula for the propagator dressed with N photons in the vacuum. Here, we extend this master formula to include a constant field. The two-photon case is worked out explicitly, yielding an integral representation for the Compton scattering cross section in the field suitable for numerical integration in the full range of electric and ma…
On the Stability of Leading-Power Factorization under Photon Propagator Numerator Modifications
该研究探讨了在光子传播子分子修改下主导功率因子分解的稳定性，表明在特定条件下因子分解形式保持不变，且背景敏感性仅在更高阶效应中显现。
Non-perturbative formalism of the generalized effective action is used for deriving the Schwinger-Dyson equations. In order to clear the domain of integration in the functional integral from gauge copies a restriction to the Gribov horizon due to Zwanziger is implemented. In this approach an asymptotic behaviour of gluon propagator and propagator of the Faddeev-Popov ghosts at small momenta is studied. Such a behaviour is obtained as a result of solving coupled Schwinger-Dyson equations in zeroth and first-order approximation. The qualitative agreement of these results with the ones obtained b…
Gauge theories play a fundamental role in particle physics, nuclear physics, and cosmology. The basic idea of these theories is that the Lagrangian density should be invariant under some transformations. Lagrangian invariance implies a certain freedom in defining gauge fields. In this study, the standard path integral quantization formalism is used. Gauge degrees of freedom manifest themselves in the difficulties in obtaining gauge field propagators. For a consistent quantization, it is necessary to eliminate non-physical gauge degrees of freedom. The standard procedure is to break the gauge s…
We study unquenched QED in four dimensions using renormalised Schwinger-Dyson equations and focus on the behaviour of the fermion and photon propagators. For this purpose we use an improved Kizilersu-Pennington (KP) vertex which respects gauge invariance, multiplicative renormalizability for the massless case, agrees with perturbation theory in the weak coupling regime and is free of kinematic singularities. We find that the KP vertex performs very well as expected specially in comparison with other vertex choices. We find that the Landau pole problem familiar from perturbative QED persists in…
The one-loop effective action of quantum electrodynamics in four dimensions is shown to be controlled by the Euclidean Dirac propagator $G$ in a background potential. After separating the photon self-energy and photon-photon scattering graphs from the effective action the remainder is known to be the logarithm of an entire function of the electric charge of order 4 under mild regularity assumptions on the potential. This input together with QED's lack of an ultrastable vacuum constrain the strong field behavior of $G$. It is shown that $G$ vanishes in the strong field limit. The relevance of t…
We solve the Minkowski-space Schwinger-Dyson equation (SDE) for the fermion propagator in quantum electrodynamics (QED) with massive photons. Specifically, we work in the quenched approximation within the rainbow-ladder truncation. Loop-divergences are regularized by the Pauli-Villars regularization. With moderately strong fermion-photon coupling, we find that the analytic structure of the fermion propagator consists of an on-shell pole and branch-cuts located in the timelike region. Such structures are consistent with the direct solution of the fermion propagator as functions of the complex m…
We consider various ways of treating the infrared divergence which appears in the dynamically generated fermion mass, when the transverse part of the photon propagator in N flavour $QED_{3}$ at finite temperature is included in the Matsubara formalism. This divergence is likely to be an artefact of taking into account only the leading order term in the $1 \over N$ expansion when we calculate the photon propagator and is handled here phenomenologically by means of an infrared cutoff. Inserting both the longitudinal and the transverse part of the photon propagator in the Schwinger-Dyson equation…
Connection of the invariant Dirac equation over the de Sitter space with irreducible representations of the de Sitter group is ascertained. The set of solutions of this equation is obtained in the form of the product of two different systems of generalized coherent states for the de Sitter group. Using these solutions the quantized Dirac field over de Sitter space is constructed and its propagator is found. It is a result of action of some de Sitter invariant spinor operator onto the spin zero propagator with an imaginary shift of a mass.
Real-time thermal photon-photon interactions in the mixed space
该研究在实时形式（RTF）下，于混合空间计算光子自能，推导热传播子，简化RTF计算并对比了相关电磁性质的结果。
Quantum de Sitter Entropy and Sphere Partition Functions: A-Hypergeometric Approach to Higher Loop Corrections
本文提出用 A-超几何级数/GKZ 系统方法将球面背景上的费曼积分化为广义欧拉积分，从而计算德西特熵的高阶圈量子修正，并推广到矢量和一般自旋场。
In the first part of this series, we employed the second-order formalism and the ``symbol'' map to construct a particle path-integral representation of the electron propagator in a background electromagnetic field, suitable for open fermion-line calculations. Its main advantages are the avoidance of long products of Dirac matrices, and its ability to unify whole sets of Feynman diagrams related by permutation of photon legs along the fermion lines. We obtained a Bern-Kosower type master formula for the fermion propagator, dressed with $N$ photons, in terms of the ``$N$-photon kernel,'' where t…
In the first part of this thesis a coupled truncated set of Dyson-Schwinger equations (DSEs) including the one for the gluon-propagator is solved self-consistently over the whole momentum range. In Landau gauge the truncation of the coupled set of DSEs for the ghost and gluon propagators is improved by the first full inclusion of the sunset diagram. A solution method which avoids all overlapping divergences is presented. In the Maximal Abelian gauge a truncation is developed with respectively one infrared and one ultraviolet leading diagram included. A first solution of the ghost equation is p…
We evaluate the propagator of scalar and spinor in three dimensional quantum electrodynamics with the use of Ward-Identity for soft-photon emission vertex.We work well in position space to treat infrared divergences in our model. Exponentiation of one-photon matrix element yields a full propagator in position space.It has a simple form as free propagator multiplied by quantum correction.And it shows a new type of mass singularity.But this is not an integrable function so that analysis in momentum space is not easy.Term by term integral converges and they have a logarithmic singularity associat…
We present a calculation of the electron mass operator combining the bubble-chain photon and the leading order electron propagators in a strong constant crossed electromagnetic field. The photon propagator is obtained by a summation of the Dyson series over 1PI polarization loop insertions and is accounted for in general form. By applying the derived mass operator, we find the bubble-chain electron propagator and the elastic scattering amplitude. The results are expressed in the general form of expansion over $γ$-matrix structures, each multiplied by a scalar invariant function of the electron…
We study the transformation of the dressed electron propagator and the general $N$-point functions under a change in the covariant gauge of internal photon propagators. We re-establish the well known Landau-Khalatnikov-Fradkin transformation for the propagator and generalise it to arbitrary correlation functions in configuration space, finding that it coincides with the analogous result for scalar fields. We comment on the consequences for perturbative application in momentum-space.
We extend the notion of generalized unitarity cuts to accommodate loop integrals with higher powers of propagators. Such integrals frequently arise in for example integration-by-parts identities, Schwinger parametrizations and Mellin-Barnes representations. The method is applied to reduction of integrals with doubled and tripled propagators and direct extract of integral coefficients at one and two loops. Our algorithm is based on degenerate multivariate residues and computational algebraic geometry.
One-loop calculations in quantum gravity coupled to U(1)-Abelian fields (photon fields) are ultraviolet finite and cutoff-free in the framework of causal perturbation theory. We compute the photon loop correction to the graviton propagator and the photon self-energy in second order perturbation theory. Perturbative gauge invariance to second order is shown and generates the gravitational Slavnov-Ward identities.
In this paper, the deformation of the Heisenberg algebra, consistent with both the generalized uncertainty principle and doubly special relativity, has been analyzed. It has been observed that, though this algebra can give rise to fractional derivative terms in the corresponding quantum mechanical Hamiltonian, a formal meaning can be given to them by using the theory of harmonic extensions of function. Depending on this argument, the expression of the propagator of the path integral corresponding to the deformed Heisenberg algebra, has been obtained. In particular, the consistent expression of…
It is well known that the long-range nature of the Coulomb interaction makes the definition of asymptotic ``in'' and ``out'' states of charged particles problematic in quantum field theory. In particular, the notion of a simple particle pole in the vacuum charged particle propagator is untenable and should be replaced by a more complicated branch cut structure describing an electron interacting with a possibly infinite number of soft photons. Previous work suggests a Dirac propagator raised to a fractional power dependent upon the fine structure constant, however the exponent has not been calc…
The notions of minimum geometrical length and minimum length scale are discussed with reference to correlation functions obtained from in-in and in-out amplitudes in quantum field theory. Whereas the in-in propagator for metric perturbations does not admit the former, the in-out Feynman propagator shows the emergence of the latter. A connection between the Feynman propagator of quantum field theories of gravity and the deformation parameter $δ_0$ of the generalised uncertainty principle (GUP) is then exhibited, which allows to determine an exact expression for $δ_0$ in terms of the residues of…
Starting from the generating functional of the theory of relativistic spinors in 2+1 dimensions interacting through the pure Chern-Simons gauge field, the S-matrix is constructed and seen to be formally the same as that of spinor quantum electrodynamics in 2+1 dimensions with Feynman diagrams having external photon lines excluded, and with the propagator of the topological Chern-Simons photon substituted for the Maxwell photon propagator. It is shown that the absence of real topological photons in the complete set of vector states of the total Hilbert space leads in a given order of perturbati…
Recently there is an alternative reduction method proposed by Chen in [1,2]. In this paper, using the one-loop scalar integrals with propagators having higher power, we show the power of the improved version of Chen's new method in which we used some tricks to cancel the dimension shift and the terms we do not want. We present the explicit examples of bubble, triangle, box and pentagon with one propagators doubled. With these results, we have completed our previous computations in \cite{wang} with the missed tadpole coefficients.
One loop expressions for fermion self energy,vacuum polarization and vertex correction in light front time ordered perturbation theory (LFTPOT) can be obtained from respective covariant expressions by performing k^- integration. In earlier work, we have shown that the third term in the doubly transverse gauge propagator is necessary to generate the diagrams involving instantaneous photon exchange both in case of fermion self-energy as well as vertex correction.In this work,we show that instantaneous photon exchange diagrams in fermion self-energy as well as th IR singular terms in the propagat…
We consider the interaction between a charged scalar boson and the Bopp-Podolsky gauge fields. The Bopp-Podolsky (BP) electrodynamics possesses both massive and massless propagation modes for the photon, while preserving gauge invariance. We obtain the propagator of all fields present in the model for the higher-order generalizations of the linear covariant, light-front and doubly transverse light-front gauges. Although BP's original model is described by a higher-order derivatives Lagrangian, it is possible to work with an equivalent reduced-order version by means of the introduction of an au…
The effect of retardation on dynamical mass generation in is studied, in the imaginary time formalism. The photon porarization tensor is evaluated to leading order in 1/N (N is the number of flavours), and simple closed form expressions are found for the fully retarded longitudinal and transverse propagators, which have the correct limit when T goes to zero. The resulting S-D equation for the fermion mass (at order 1/N) has an infrared divergence associated with the contribution of the transverse photon propagator; only the longitudinal contribution is retained, as in earlier treatments. For s…
Feynman Propagator of the Arthurs-Kelly system at the Planck Scale
本文在Arthurs-Kelly系统中引入广义不确定性原理，精确推导出一阶GUP参数下的费曼传播子，并简要探讨其在早期宇宙中的应用。
We use the worldline representation for correlation functions together with numerical path integral methods to extract nonperturbative information about the propagator to all orders in the coupling in the quenched limit (small-$N_{\text{f}}$ expansion). Specifically, we consider a simple two-scalar field theory with cubic interaction (S${}^2$QED) in four dimensions as a toy model for QED-like theories. Using a worldline regularization technique, we are able to analyze the divergence structure of all-order diagrams and to perform the renormalization of the model nonperturbatively. Our method gi…
We here consider a generalization of the Klein-Gordon scalar wave equation which involves a single arbitrary function. The quantization may be viewed as allowing $\hbar$ to be a function of the momentum or wave vector rather than a constant. The generalized theory is most easily viewed in the wave vector space analog of the Lagrangian. We need no reference to spacetime. In the generalized theory the de Broglie relation between wave vector and momentum is generalized, as are the canonical commutation relations and the uncertainty principle. The generalized uncertainty principle obtained is the …
Exact results, transient generalized Gibbs ensembles, and analytic approximations for spacetime propagators of massive, real scalar fields in one spatial dimension
本文全面研究一维大质量实标量场传播子，重新推导精确结果，引入瞬态广义吉布斯系综理解，并给出仅含初等函数的解析近似。
In the first-quantised worldline approach to quantum field theory, a long-standing problem has been to extend this formalism to amplitudes involving open fermion lines while maintaining the efficiency of the well-tested closed-loop case. In the present series of papers, we develop a suitable formalism for the case of quantum electrodynamics in vacuum (part one and two) and in a constant external electromagnetic field (part three), based on second-order fermions and the symbol map. We derive this formalism from standard field theory, but also give an alternative derivation intrinsic to the worl…
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