Daniel H. T. Franco, André H. Gomes
We report on our current progress in the study of finite one-loop radiative corrections in the minimal Lorentz- and CPT-violating QED extension.
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We discuss the regularization and renormalization of QED with Lorentz and CPT violation, and argue that the coefficient of the Chern-Simons term is an independent parameter not determined by gauge invariance. We also study these issues in a model with spontaneous breaking of Lorentz and CPT symmetries and find an explicit relation with the ABJ anomaly. This explains the observed convergence of the induced Chern-Simons term.
We investigate the breakdown of Lorentz symmetry in QED by a CPT violating interaction term consisting of the coupling of an axial fermion current with a constant vector field $b$, in the framework of algebraic renormalization -- a regularization-independent method. We show, to all orders in perturbation theory, that a CPT-odd and Lorentz violating Chern-Simons-like term, definitively, is not radiatively induced by the axial coupling of the fermions with the constant vector $b$.
We rediscuss the controversy on a possible Chern-Simons like term generated through radiative corrections in QED with a CPT violating term. We analyse some consequences of the division of the Lagrangian density between "free part" and "interaction part". We also emphasize the fact that any absence of an {\sl a priori} divergence should be explained by some symmetry or some non-renormalisation theorem and show that the so-called "unambiguous result" based upon "maximal SO(3) residual symmetry " does not offer a solution.
We analyse the recent controversy on a possible Chern-Simons like term generated through radiative corrections in QED with a CPT violating term : we prove that, if the theory is correctly defined through Ward identities and normalisation conditions, no Chern-Simons term appears, without any ambiguity. This is related to the fact that such a term is a kind of minor modification of the gauge fixing term, and then no renormalised. The past year literature on that subject is discussed, and we insist on the fact that any absence of an {\sl a priori} divergence should be explained by some symmetry o…
Two-loop corrections to the Carroll-Field-Jackiw term in a CPT-odd Lorentz-violating scalar QED
本文在CPT奇量子电动力学框架下系统计算了Lorentz破坏顶点的单圈修正，并确定了Carroll-Field-Jackiw项的有限双圈修正及标量场自能的紫外发散分量。
We consider the process of photon decay in quantum electrodynamics with a CPT-violating Chern-Simons-like term added to the action. For a simplified model with only the quadratic Maxwell and Chern-Simons-like terms and the quartic Euler-Heisenberg term, we obtain a nonvanishing probability for the decay of a particular photon state into three others.
Scale anomaly in a Lorentz and CPT-violating Quantum Electrodynamics
该研究计算最小洛伦兹和CPT破缺量子电动力学中伸缩流的经典与量子破缺，明确质量项、类Chern-Simons项及无质量极限下费米子算符对尺度对称性的作用。
The Lorentz invariant $CPT$ violation by using non-local interactions is naturally incorporated in the Higgs coupling to neutrinos in the Standard Model, without spoiling the basic $SU(2)_{L}\times U(1)$ gauge symmetry. The neutrino--antineutrino mass splitting is thus realized by the mechanism which was proposed recently, assuming the neutrino masses to be predominantly Dirac-type in the Standard Model.
A theoretical framework extending QED in the context of the standard model is used to analyze a variety of Lorentz and CPT tests in atomic systems. Experimental signatures of possible Lorentz and CPT violation in these systems are investigated, and bounds are discussed.
The general features of renormalization and the renormalization group in QED and in general quantum field theories in curved spacetime with additional Lorentz- and CPT-violating background fields are reviewed.
This talk summarizes some theoretical features and experimental implications of a general Lorentz-violating extension of the minimal SU(3) x SU(2) x U(1) standard model that allows for both CPT-even and CPT-odd effects. The theory would arise as the low-energy limit of a fundamental theory that is Lorentz and CPT covariant but in which spontaneous Lorentz breaking occurs. The use of neutral-meson oscillations and various QED systems to bound the apparent CPT and Lorentz violations is described.
We investigate an alternative CPT-odd Lorentz-breaking QED which includes the Carroll-Field-Jackiw (CFJ) term of the Standard Model Extension (SME), writing the gauge sector in the action in a Palatini-like form, in which the vectorial field and the field-strength tensor are treated as independent entities. Interestingly, this naturally induces a Lorentz-violating mass term in the classical action. We study physical consistency aspects of the model both at classical and quantum levels.
The strongest bounds on some forms of Lorentz and CPT violation come from astrophysical data, and placing such bounds may require understanding and modeling distant sources of radiation. However, it is also desirable to have bounds that do not rely on these kinds of detailed models. Bounds that do not rely on any modeling of astrophysical objects may be derived both from laboratory experiments and certain kinds of astrophysical observations. The strongest such bounds on isotropic modifications of electron, positron, and photon dispersion relations of the form E^2 = p^2 + m^ 2 + epsilon p^3 com…
We investigate models described by real scalar fields, searching for defect structures in the presence of interactions which explicitly violate Lorentz and CPT symmetries. We first deal with a single field, and we investigate a class of models which supports traveling waves that violate Lorentz invariance. This scenario is then generalized to the case of two (or more) real scalar fields. In the case of two fields, in particular, we introduce another class of models, which supports topological structures that attain a Bogomol'nyi bound, although violating both Lorentz and CPT symmetries. An exa…
In this paper we evaluate the induced Lorentz and CPT violating Chern-Simons term in the QED action at finite temperature. We do this using the method of derivative expansion of fermion determinants. Also, we use the imaginary-time formalism to calculate the temperature dependence of the Chern-Simons term
We have studied the contributions of Lorentz-violating CPT-odd and CPT-even nonminimal couplings to the energy spectrum of the mesonic hydrogen and the higher-order radiative corrections to the effective action of the photon sector of a Lorentz-violating version of the scalar electrodynamics. By considering the complex scalar field describes charged mesons (pion or kaon), the non-relativistic limit of the model allows to attain upper-bounds by analyzing its contribution to the mesonic hydrogen energy. By using the experimental data for the $1S$ strong correction shift and the pure QED transiti…
We study the Lorentz and CPT violating effects on the branching ratio BR, the CPT violating asymmetry A_{CPT} and the ratio of the decay width, including only the Lorentz violating effects, to the one obtained in the standard model, for the flavor dependent part of the lepton flavor conserving Z\to l^+ l^- (l=e,μ,τ) decay. The inclusion of the Lorentz and CPT violating effects to the standard model contribution is too small to be detected, since the corresponding coefficients are highly suppressed at the low energy scale.
We obtain the induced Lorentz- and CPT-violating term in QED at finite temperature using imaginary-time formalism and dimensional regularization. Its form resembles a Chern-Simons-like structure, but, unexpectedly, it does not depend on the temporal component of the fixed $b_μ$ constant vector that is coupled to the axial current. Nevertheless Ward identities are respected and its coefficient vanishes at T=0, consistently with previous computations with the same regularization procedure, and it is a non-trivial function of temperature. We argue that at finite $T$ a Chern-Simons-like Lorentz- a…
We analyse some dimension-five CPT-even and Lorentz-violating nonminimal couplings between fermionic and gauge fields in the context of the Dirac equation. After evaluating the nonrelativistic Hamiltonian, we discuss the behavior of the terms under discrete symmetries and analyse the implied effects. We then use the anomalous magnetic dipole moment and electron electric dipole moment measurements to reach upper bounds of $1$ part in $10^{20}$ and $10^{24}$ $\left( eV\right) ^{-1}$, improving the level of restriction on such couplings by at least 8 orders of magnitude. These upper bounds are al…
In this work, we consider the Hořava-Lifshitz scaling to rewrite higher-order derivatives in Lorentz-violating CPT-even electrodynamics. The possibility of the Lorentz invariance violation being originally suppressed by the quantum gravity energy scale $M_{\rm QG}$, may be indeed circumvented in a scenario with anisotropy between space and time above certain intermediate energy scale $Λ_{\rm HL} \ll M_{\rm QG}$. To test the model, we have used observational results of a cosmological time delay between high and low energy photons from gamma ray bursts (GRB090510) event. For specific values of t…
A brief summary is given of recent developments concerning a Lorentz-violating extension of the standard model and its implications for experiments testing Lorentz and CPT symmetry.
We consider low-energy CPT-violating modifications in charged current weak interactions and analyze possible ramifications in muon and antimuon decays. We calculate the lifetime of muon and antimuon with these modifications, and from the result, put bounds on the CPT-violating parameters. Moreover, we elaborate on the muon and antimuon decay rate differentials in electron energy and spatial angle, which entail interesting phenomenological consequences presenting new ways to constrain CPT violation in charged lepton decays.
We study the Lorentz and CPT violating effects on the branching ratio and the CP violating asymmetry of the lepton flavor violating interactions μ\to eγand τ\to μγ, in the model III version of the two Higgs doublet model. Here we consider that the Lorentz and CPT violating effects exist in the QED part of the interactions and enter into expressions in the lepton propagators and in the lepton-photon vertex. We observe that there exists a non-zero CP asymmetry. However, the Lorentz and CPT violating effects on the braching ratio and the CP asymmetry are negligibly small.
In Lorentz- and CPT-violating effective field theories involving scalar and spinor fields, there exist forms of Lorentz violation that modify only the scalar-spinor Yukawa interaction vertices. These affect low-energy fermion and antifermion scattering processes through modifications to the nonrelativistic Yukawa potentials. The modified potentials involve novel combinations of momentum, spin, and Lorentz-violating background tensors.
We study the decay widths of the processes H^+\to W^+ H^0 (h^0,A^0), including the Lorentz violating effects and analyze the possible CPT violating asymmetry arising from CPT odd coefficients. We observe that these effects are too small to be detected, since the corresponding coefficients are highly suppressed at the low energy scale.
In a temperature dependent CPT-Violating (CPTV) axial time-like background (induced by the Kalb-Ramond tensor field of string theory) we discuss leptogenesis by solving the Boltzmann equation.The current work non-trivially modifies the framework of a previous phenomenological approach by the authors where the CPTV axial background was considered to be a constant (with no microscopic justification). The constant background approximation though is shown to capture the main phenomenological features of leptogenesis. On comparing our analysis to the related chiral magnetic effect for axial current…
We consider quantum electrodynamics with an additional Lorentz- and CPT-violating axial-vector term in the fermionic sector and discuss the possibility that radiative corrections induce a Lorentz- and CPT-violating Chern-Simons-like term for the gauge field. From the requirement of causality and the assumed validity of perturbation theory, we conclude that the induced Chern-Simons-like term must be absent in the full quantum field theory.
We show that the general Lorentz- and CPT-violating extension of quantum electrodynamics is one-loop renormalizable. The one-loop Lorentz-violating beta functions are obtained, and the running of the coefficients for Lorentz and CPT violation is determined. Some implications for theory and experiment are discussed.
Symmetry breaking induced by untwisted fermions in QED in a nonsimply connected spacetime with topology $S^{1}\times R^{3}$ is investigated. It is found that the discrete CPT symmetry of the theory is spontaneously broken by the appearance of a constant vacuum expectation value of the electromagnetic potential along the direction of space periodicity. The constant potential is shown to be gauge nonequivalent to zero in the nonsimply connected spacetime under consideration. Due to the symmetry breaking, one of the electromagnetic modes of propagation is massive with a mass that depends on the i…
We present a general model-independent formalism of measuring CP and CPT violating parameters through time-ordered integrated rates of correlated decays of $C=\pm 1$ entangled states of neutral pseudoscalar mesons. We give the general formulae of CP and CPT violating parameters in terms of four measurable asymmetries defined for the time-ordered integrated rates, applicable to all kinds of decay product. Two special cases which are often realized in experiments are discussed specifically.
Lorentz and CPT violation in hadronic physics must be tied to symmetry violations at the underlying quark and gluon level. Chiral perturbation theory provides a method for translating novel operators that may appear in the Lagrange density for color-charged parton fields into equivalent forms for effective theories at the meson and baryon levels. We extend the application of this technique to the study of Lorentz-violating and potentially CPT-violating operators from the minimal standard model extension. For dimension-4 operators, there are nontrivial relations between the coefficients of bary…
The combination Charge Conjugation-Parity-Time Reversal(CPT) is a fundamental symmetry in our current understanding of nature. As such, testing CPT violation is a strongly motivated path to explore new physics. In this paper we study CPT violation in the neutrino sector, giving for the first time a bound, for a fundamental particle, in the CPT violating particle-antiparticle gravitational mass difference. We argue that cosmology is nowadays the only data sensitive to CPT violation for the neutrino-antineutrino mass splitting and we use the latest data release from Planck combined with the curr…
A possibility of a verification of CPT-invariance of QED for bound states by example of muonium or antimuonium produced in reactions of scattering of electrons or positrons by nuclei is considered. The number of events of the muonium production is estimated for contemporary accelerators. The method of the detection of muonium by measuring of oscillations of the decay curve caused by the interference between the ground and excited state of muonium is suggested. The admixture of the excited muonium to the final state is calculated.
Radiative corrections arising from Lorentz violation in the fermion sector induce a nonzero amplitude for vacuum photon splitting. At one loop, the on-shell amplitude acquires both CPT-even and CPT-odd contributions forbidden in conventional electrodynamics.
Considering that the existing experimental limit for $CPT$ violation is still poor, we explore various possible ways to test $CPT$ symmetry in $CP$-violating $B$ decays at $e^{+}e^{-}$ $B$ factories. We find that it is difficult to distinguish between the effect of direct $CP$ violation and that of $CPT$ violation in the time-integrated measurements of neutral $B$ decays to $CP$ eigenstates such as $ψK_{S}$ and $π^{+}π^{-}$. Instead, a cleaner signal of small $CPT$ violation may appear in the time-integrated $CP$ asymmetries for a few non-$CP$-eigenstate channels, e.g., $B^{0}_{d}/\bar{B}^{0}_…
We review the status of CPT violation in the neutrino sector. Apart from LSND, current data favors three flavors of light stable neutrinos and antineutrinos, with both halves of the spectrum having one smaller mass splitting and one larger mass splitting. Oscillation data for the smaller splitting is consistent with CPT. For the larger splitting, current data favor an antineutrino mass-squared splitting that is an order of magnitude larger than the corresponding neutrino splitting, with the corresponding mixing angle less-than-maximal. This CPT-violating spectrum is driven by recent results fr…
We show a simple mechanism for a dynamical CPT violation in the neutron sector. In particular, we show a {\it CPT-violating see-saw mechanism}, generating a Majorana mass and a CPT violating mass for the neutron. CPT-violating see-saw involves a sterile partner of the neutron, living in a hidden sector, in which CPT is spontaneously broken. In particular, neutrons (antineutrons) can communicate with the hidden sector through non-perturbative quantum gravity effects called {\it exotic instantons}. Exotic instantons dynamically break R-parity, generating one effective vertex between the neutron …
Considering that the existing experimental limit for $CPT$ violation is still poor, we explore various possible ways to test $CPT$ symmetry in $CP$-violating $B$ decays at $e^{+}e^{-}$ $B$ factories and hadron machines. We find that it is difficult to distinguish between the effect of direct $CP$ violation and that of $CPT$ violation in the time-integrated measurements of neutral $B$ decays to $CP$ eigenstates such as $ψK_{S}$ and $π^{+}π^{-}$. Instead, a cleaner signal of small $CPT$ violation may appear in the time-integrated $CP$ asymmetries for a few non-$CP$-eigenstate channels, e.g., $B^…
The possibility of a small modification of spinor Quantum Electro-Dynamics is reconsidered, in which Lorentz and CPT non-covariant kinetic terms for photons and fermions are present. The corresponding free field theory is carefully discussed. The finite one-loop parity-odd induced effective action is unambiguously calculated using the physical cutoff method, which manifestly encodes the maximal residual symmetry group allowed by the presence of the Lorentz and CPT breaking axial-vector. This very same induced effective action, which is different from those ones so far quoted in the Literature,…
We present a general model-independent and rephase-invariant formalism that cleanly relates CP and CPT noninvariant observables to the fundamental parameters. Different types of CP and CPT violations in the K^0-, B^0-, B_s^0- and D^0-systems are explicitly defined. Their importance for interpreting experimental measurements of CP and CPT violations is emphasized. In particular, we show that the time-dependent measurements allow one to extract a clean signature of CPT violation.
We study the Lorentz and CPT violating effects on the ratio \frac{BR_{LorVio}}{BR_{SM}}, where BR_{LorVio} (BR_{SM}) is the branching ratios coming from the Lorentz violating effects (the SM), for the decays H^0\to f^+ f^- (f= quarks and charged leptons) and H^0\to ZZ (W^+ W^-). We observe that these new effects are too small to be detected, especially for f^+ f^- output, since the corresponding coefficients are highly suppressed at the low energy scale.
A class of calculable global models for neutrino oscillations based on Lorentz and CPT violation is presented. One simple example matches established neutrino data from accelerator, atmospheric, reactor, and solar experiments, using only two degrees of freedom instead of the usual five. A third degree of freedom appears in the model, and it naturally generates the MiniBooNE low-energy anomalies. More involved models in this class can also accommodate the LSND anomaly and neutrino-antineutrino differences of the MINOS type. The models predict some striking signals in various ongoing and future …
CPT-Violating photons are well-known to have problems with energy positivity in certain cases and therefore have not been convincingly quantized to date. We find that by adding a small mass term, consistent with experimental bounds, the theory can be regulated and allows for a consistent covariant quantization procedure. This new framework is applied to a consistent quantum calculation of vacuum Cherenkov radiation rates. These rates turn out to be largely independent of the mass of the photon regulator used. In the physical regime, accessible by ultra high energy cosmic rays, the behavior of …
We propose a simple phenomenological model predicting, through Lorentz symmetry breaking, a CPT-violating asymmetry between particle and antiparticle states in neutrino oscillations involving sterile neutrinos. Such a model is able to explain the apparently observed anomalous excess of low-energy ν_e-like events, reported by the MiniBooNE collaboration, as well as the non-observation of the corresponding anomalous excess of \ovν_e-like events. The present model leads to very specific physical predictions in the neutrino oscillations scenario, and account for the observed anomalies in terms of …
A theoretical study of possible signals for CPT and Lorentz violation arising in hydrogen and antihydrogen spectroscopy is described. The analysis uses a CPT- and Lorentz-violating extension of quantum electrodynamics, obtained from a general Lorentz-violating extension of the minimal standard model with both CPT-even and CPT-odd terms. Certain 1S-2S transitions and hyperfine Zeeman lines exhibit effects at leading order in small CPT-violating couplings.
We perform the covariant canonical quantization of the CPT- and Lorentz-symmetry-violating photon sector of the minimal Standard-Model Extension, which contains a general (timelike, lightlike, or spacelike) fixed background tensor $k_{AF}^μ$. Well-known stability issues, arising from complex-valued energy states, are solved by introducing a small photon mass, orders of magnitude below current experimental bounds. We explicitly construct a covariant basis of polarization vectors, in which the photon field can be expanded. We proceed to derive the Feynman propagator and show that the theory is m…
A model for spontaneous symmetry breaking using a specific form of the bumblebee model is analyzed in the context of a Schwarzschild background metric. The resulting back reaction of the symmetry-breaking field on the metric is computed to second order. Consistency with conventional (pseudo)Riemannian geometry is demonstrated. This background field is coupled to fermions via a spin-dependent CPT-violating coupling term of a type commonly considered in the Standard-Model Extension. The perturbations of various orbital trajectories are discussed. Specifically, a spin-dependent orbital velocity i…
CPT violation in the neutrino sector, suggested as a new way to reconcile different neutrino anomalies, induces at the radiative level observable effects among charged leptons, where high-precision tests of the CPT symmetry are available. We show that, in the models with heavy right-handed Majorana neutrinos, constraints imposed by these experiments require CPT violation in neutrino spectrum be suppressed to a level undetectable for any conceivable neutrino experiment. We find that the CPT violation in the neutrino sector may evade indirect constraints only at the expense of light right-handed…
We study the status of the CPT violating neutrino mass spectrum which has been proposed to simultaneously accommodate the oscillation data from LSND, KamLAND, atmospheric and solar neutrino experiments, as well as the non-observation of anti-neutrino disappearance in short-baseline reactor experiments. We perform a three-generation analysis of the global data with the aim of elucidating the viability of this solution. We find no compatibility between the results of the oscillation analysis of LSND and all-but-LSND data sets below 3$σ$ CL. Furthermore, the global data without LSND show no evide…
Interplay of CPT-Violating and CPT-Conserving Lorentz Invariance Violation at DUNE
研究中微子振荡里洛伦兹不变性破坏，重点关注CPT相关系数相互作用，以DUNE为实验，发现对角与非对角LIV系数影响不同，其存在削弱CP破坏敏感性，强调长基线实验精确振荡研究中纳入LIV效应的重要性。
The radiatively induced Lorentz and CPT violating Chern-Simons terms in QED is calculated based on the recently developed loop regularization method [Y.L. Wu, Int.J.Mod.Phys.A18 (2003) 5363, hep-th/0209021; Y.L. Wu, Mod.Phys.Lett.A19 (2004) 2191, hep-th/0311082] for quantum field theories. It enables us to make general comments on the various results in literature and obtain a consistent result when simultaneously combining the evaluation for the chiral anomaly which has a unique form once the vector current is kept conserved.
We show that a hierarchical CPT violating neutrino spectrum can simultaneously accommodate all published neutrino data, including the LSND result, with a total chi^2 which is almost identical to the CPT conserving best fit. In our scenario the oscillation signal seen by the KamLAND experiment in antineutrinos is independent of the LMA solar oscillation signal seen in neutrinos. A larger antineutrino mass splitting accounts for the LSND signal and also contributes to atmospheric oscillations. Because of this feature, there is some tension between our model and certain Super-K atmospheric result…
A search is presented for CPT-violating effects in the mixing of $B^0_s$ mesons using the D0 detector at the Fermilab Tevatron Collider. The CPT-violating asymmetry in the decay $B^0_s \rightarrow μ^{\pm} D_s^{\mp} X$ as a function of sidereal phase is measured. No evidence for CPT-violating effects is observed and limits are placed on CPT- and Lorentz-invariance violating coupling coefficients.
In this paper, we examine the CP-violating term of the Euler-Heisenberg action. We focus in the aspects related with the generation of such a term from a QED-like model in terms of the effective action approach. In particular, we show that the generation of the CP-violating term is closely related with both of vector and axial fermionic bilinears. Although, these anomalous models are not a "viable" extension of QED, we argue that the CP-violating term in the photon sector is obtained only from this class of models, and not from any fundamental field theory.
Assuming that CPT is violated in the neutrino sector seems to be a viable alternative to sterile neutrinos when it comes to reconciling the LSND anomaly with the remainder of the neutrino data. There are different (distinguishable) ways of incorporating CPT violation into the standard model, including postulating m different from \bar{m}. Here, I investigate the possibility of introducing CPT violation via Lorentz-invariance violating effective operators (``Ether'' potentials) which modify neutrino oscillation patterns like ordinary matter effects. I argue that, within a simplified two-flavor …
In this talk, I discuss possible bounds on the Lorentz and CPT violating parameters in the Higgs sector of the so called minimal standard model extension. The main motivation to this study is coming from the fact that unlike the parameters in the fermion and gauge sector, there are no published bounds on the parameters in the Higgs sector. From the one-loop contributions to the photon propagator the bounds on the CPT-even asymmetric coefficients are obtained and the c_μνcoefficients in the fermion sector determine the bound on the CPT-even symmetric coefficients. The CPT-odd coefficient is bou…
The electrodynamics with a Chern-Simons term $p_μA_ν\widetilde{F}^{μν}$ violates Lorentz and $CPT$ symmetries with a non-vanishing $p_μ$. For a fixed vector $p_μ$, in this paper we point out that the energy-momentum tensor of this theory coupled to the gravity minimally is symmetric but not divergence free, which consequently makes the gravitational field equation inconsistent. To preserve the consistency, we introduce a Chern-Simons term in the gravity sector with the coefficient determined by the Lorentz and $CPT$ violating term in the electromagnetic field. Further we study the phenomenolog…
Analytical solutions with effective CPT-violating spin--gravity corrections to the neutron's gravitational bound states are obtained. The helicity-dependent phase evolution due to $\vecσ\cdot\vec{\tilde{b}}$ and $\vecσ\cdot\hat{\vec{p}}$ couplings not only leads to spin precession, %shown by the tip of the spin on the Bloch sphere,but also to transition-frequency shifts between different gravitational bound states. Utilizing transition frequencies measured in the qBounce experiment,\cite{GRS} we obtain the rough bound $|\vec{\tilde{b}}|<6.9\times10^{-21}$GeV. Incorporating known systematic err…
Stringent limits on the Myers-Pospelov timelike parameter for photons $ξ<10^{-15}$ coming from astrophysical tests suggest exploring more general preferred backgrounds, such as spacelike and lightlike. We take some steps in this direction. We allow the external four vector $n$ characterizing the Lorentz symmetry breaking to have arbitrary directions in spacetime. We study the consistency for the effective field theories in each privileged frame by demanding causality, stability and analyticity. When specializing to a timelike background we found runaway solutions leading to causality and unita…
The unitarity in Lorentz invariance violating QED consisting of standard fermions and higher-order photons of the Myers-Pospelov theory is studied. We find ghost states associated to the higher-order character of the theory which could render the $S$ matrix nonunitary. An explicit calculation to check perturbative unitarity in the process of electron-positron scattering is performed and it is found to be possible to preserve unitarity.
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