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We study electromagnetic radiation by electrically charged fermions embedded in a rotating medium in an external magnetic field. We compute the dependence of the radiation intensity on the angular velocity $\Omega$ of the rotating medium for fermion polarizations along and opposite the magnetic field direction in intense subcritical fields. The polarization dependence of the photon radiation results in the Sokolov--Ternov effect -- the radiative polarization of fermions. We study the dependence of the degree of polarziation on $\Omega$. We found that rotation significantly changes the degree of polarization. We show that the rotating quark-gluon plasma acquires a finite magnetic moment that exhibits complex dependence on $\Omega$., Comment: 18 pages

The emergent axion excitations in the quark-gluon plasma are generated by the sphaleron transitions. Their interactions with the photon and gluon fields are governed by the axion electro- and chromodynamics respectively. We discuss the effect of the emergent axion on the photon production and energy loss in the quark-gluon plasma. In particular, we review the Chiral Cherenkov effect, and the impact of the chiral anomaly on bremsstrahlung., Comment: Review for International Journal of Modern Physics E

We consider the Dirac field uniformly rotating with angular velocity $\Omega$ and also subject to the constant magnetic field $B$ directed along the rotation axis. The causal states are constrained to the interior of the light cylinder of radius $c/\Omega$. When this radius is smaller than the system size, as in the quark-gluon plasma, the effect of the boundary on the fermion spectrum is critical. We derive the fermion spectrum and study its properties. We compute the intensity of the electromagnetic radiation emitted due to transitions between the fermion states. We study its dependence on energy and angular momentum for different values of the angular velocity and the magnetic field. Rotation has enormous impact on the electromagnetic radiation by the quark-gluon plasma with or without the magnetic field., Comment: 38 pages, 16 figures; v2 published version

We propose to use the electromagnetic radiation induced by a few MeV electron beam in magnetic Weyl semimetals as a source of the circularly polarized photons in the THz frequency range.

We introduce and investigate the Color Chiral Cherenkov effect which consists in radiation of the circularly polarized gluons by a fast color charge moving with constant velocity in the presence of the Chiral Magnetic current. We derive the transition rates for all gluon polarizations. We compute the contribution of the Color Chiral Cherenkov effect to the parton energy loss in the quark-gluon plasma., Comment: 11 pages, 3 figures; v2: references and acknowledgments added, typos fixed

We consider a system rotating at extremely high angular velocity, so that its matter is found mostly at the light-cylinder. We posit that it can be described by quantum fields confined to the two-dimensional cylindrical surface rotating about its symmetry axis. We apply this model to study the electromagnetic radiation. In particular, we compute the photon spectrum emitted by the quark-gluon plasma., Comment: 15 pages, 6 figures. v2: typos and minor errors fixed

We study electromagnetic radiation by a fast particle carrying electric charge in chiral medium. The medium is homogeneous and isotropic and supports the chiral magnetic current which renders the fermion and photon states unstable. The instability manifests as the chirality-dependent resonances in the bremsstrahlung cross section, which enhance the energy loss in the chiral medium. We compute the corresponding cross sections in the single scattering approximation and derive the energy loss in the high energy approximation., Comment: 19 pages, 3 figures; v2: a technical issue with fig 1 fixed

We study the electromagnetic radiation by a fermion carrying an electric charge $q$ embedded in a medium rotating with constant angular velocity $\bf\Omega$ parallel or anti-parallel to an external constant magnetic field $\bf B$. We assume that the rotation is "relatively slow"; namely, that the angular velocity $\Omega$ is much smaller than the inverse magnetic length $\sqrt{qB}$. In practice, such angular velocity can be extremely high. The fermion motion is a superposition of two circular motions: one due to its rigid rotation caused by forces exerted by the medium, another due to the external magnetic field. We derive an exact analytical expression for the spectral rate and the total intensity of this type of synchrotron radiation. Our numerical calculations indicate very high sensitivity of the radiation to the angular velocity of rotation. We show that the radiation intensity is strongly enhanced if $q\bf B$ and $\bf \Omega$ point in the opposite directions and is suppressed otherwise., Comment: 35 pages, 10 Figures; v2: minor errors fixed

We compute the chiral magnetic effect (CME) in a cylindrical region coaxial with the external magnetic field. As the boundary condition we require vanishing of the radial component of the electric current on the cylinder side wall. We find that when the magnetic length is comparable to or larger than the cylinder radius, the CME is suppressed compared to the corresponding result in an infinite medium. As a result, for a given cylinder radius, the suppression is stronger in weak fields. We argue that the electric current generated by the CME vanishes at the cylinder wall and monotonically increases toward the symmetry axis., Comment: 13 pages, 6 figures, final version published in PRD, typos

We compute the effect of rigid rotation on the non-relativistic bound states. The energy levels of the bound states increase with the angular velocity of rotation until at certain value of the angular velocity they are completely pushed out into the continuum which corresponds to dissociation of the bound states. When the angular velocity exceeds the critical value at which the ground state disappears into the continuum, no bound state is possible. This effect should have important consequences for the phenomenology of the quark-gluon plasma. One of the ways to study it experimentally is to observe the electromagnetic radiation emitted by a rotating bound state. We compute the corresponding intensity of electromagnetic radiation and show that it strongly depends on the angular velocity of rotation., Comment: 13 pages, 5 figures

We study the synchrotron radiation emitted by a charged fermion, rotating as a part of a larger system, in a constant magnetic field $B$ parallel to the axis of rotation. The rotation is classical and independent of the magnetic field. The angular velocity of rotation $\Omega$ is assumed to be much smaller than the inverse magnetic length $\sqrt{qB}$ which allows us to ignore the boundary effects at $r=1/\Omega$. We refer to such rotation as slow, even though in absolute value it may be an extremely rapid rotation. Using the exact solution of the Dirac equation we derived the intensity of electromagnetic radiation, its spectrum and chirality. We demonstrate by explicit numerical calculation that the effect of rotation on the radiation intensity increases with the particle energy. Depending on the relative orientation of the vectors $\bf\Omega$ and $\bf B$ and the sign of the electric charge, the rotation can either strongly enhance or strongly suppress the radiation., Comment: 5 pages, 3 figures. V2: minor text improvements, Figs 1,2 updated, new Fig 3. V3: reference line in Fig.2 corrected; v4: the sign of qB in figure captions and elsewhere corrected

We investigate photon bremsstrahlung in chiral media. The chiral medium response to the magnetic field is described by the chiral magnetic current $ j= b_0 B$, where $b_0$ is the chiral magnetic conductivity. This current modifies the photon dispersion relation producing a resonance in the scattering amplitude. We show that the resonant contribution is proportional to the magnetic moment $\mu$ of the target nucleus. We analytically compute the corresponding cross section. We argue that the anomalous contribution is enhanced by a factor $b_0^2/\Gamma^2$, where $\Gamma$ is a width of the resonance related to the chiral magnetic instability of the electromagnetic field. The most conspicuous feature of the anomalous contribution to the photon spectrum is the emergence of the knee-like structure at photon energies proportional to $b_0$. We argue that the phenomenological significance of the anomalous terms depends on the magnitude of the ratio of $b_0$ to the projectile fermion mass., Comment: 16 pages, 6 figures; v2: discussion added; v3: typo in (A5) fixed

Magneto-rotational dissociation is the decay, by the way of tunneling, of a rotating bound state in the magnetic field. The corresponding probability was recently computed in the quasi-classical approximation using the Imaginary Time Method and was shown to increase with the angular velocity and decrease with the magnetic field strength \cite{Tuchin:2021lxl}. This letter reports the calculation of the quantum correction to the dissociation probability associated with the spin of the tunneling particle. The quasi-classical motion of spin is described by the Bargmann--Michel--Telegdi equation in the rotating frame. It is shown that the spin contribution significantly increases the dissociation probability. Applications to the Quark-Gluon Plasma are touched upon., Comment: 11 pages, 12 figures, v3: typos corrected, comments added. arXiv admin note: text overlap with arXiv:2102.10659

In heavy-ion collisions the electromagnetic field exists before the hot nuclear matter emergence. Requiring the field continuity we compute it in the central rapidity region by taking into account the electromagnetic response of the Quark Gluon Plasma. We show that the electromagnetic field is nearly time-independent from about 1~fm/c after the collision until the freezeout., Comment: 11 pages, 4 figures

A heavy hadron traversing Quark-Gluon Plasma and dragged along in rotational motion is subject to the Lorentz and centrifugal forces. The Lorentz force, sourced by the valence quarks of heavy-ions, possesses the electric and magnetic components in the hadron comoving frame. The electric component renders the hadron unstable by empowering one of its quarks to tunnel through the potential barrier. Assuming that the magnetic field is parallel to the plasma vorticity, the hadron dissociation probability is computed using the Imaginary Time Method and is found to strongly depend on the sign of the quark electric charge. The dissociation probability monotonically increases as a function of vorticity for negative electric charges, whereas for positive charges it exhibits a minimum at a finite value of vorticity. The dissociation probability for the negative charges is larger than for the positive ones at the same magnetic field and vorticity. In relativistic heavy-ion collisions this implies lower abundance of the negatively charged hadrons as compared to the positively charges ones. This effect is significant at moderate collision energies where the plasma vorticity is comparable or larger than the synchrotron frequency., Comment: 13 pages, 4 figures; v2: expanded and corrected

Collisional energy loss of a fast particle in a medium is mostly due to the medium polarization by the electromagnetic fields of the particle. A small fraction of energy is carried away by the Cherenkov radiation. In chiral medium there is an additional contribution to the energy loss due to induction of the anomalous current proportional to the magnetic field. It causes the particle to lose energy mostly in the form of the \emph{chiral} Cherenkov radiation. We employ classical electrodynamics, adequate in a wide range of particle energies, to compute the collisional energy loss by a fast particle in a homogenous chiral plasma and apply the results to Quark-Gluon Plasma and a Weyl semimetal. In the later case photon spectrum is strongly enhanced in the ultraviolet and X-ray regions which makes it amenable to experimental investigation. Our main observation is that while the collisional energy loss in a non-chiral medium is a slow, at most logarithmic, function of energy $E$, the chiral Cherenkov radiation is proportional to $E^2$ when the recoil is neglected and to $E$ when it is taken into account., Comment: 13 pages, 2 figures

We discuss a new channel of photon emission from the quark-gluon plasma, which opens up as photon acquires a tachyonic mass in the presence of the CP-odd topological domains generated by the chiral anomaly. It allows photon radiation through the decay $q\to q\gamma$ and annihilation $q\bar q\to \gamma$ processes closely related to the chiral Cherenkov radiation. Unlike previous proposals this mechanism does not require an external magnetic field. The differential photon emission rate per unit volume is computed and shown to be comparable to the rate of photon emission in conventional processes., Comment: contribution to the "10th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions"

The idea that the nuclear matter may posses long range topological order is supported by the theory and the lattice calculations. At high temperature this order is instrumental in producing anomalous phenomena such as the Chiral Magnetic Effect. In the cold nuclear matter it affects the gluon distribution in the nuclear wave function at low $x$. The effect of the topological order is encapsulated in the unintegrated gluon distribution functions which are proportional, at the leading order, to the square of the gluon propagator at finite topological charge density. It is argued that the Electron Ion Collider is well suited to study the topological order of the cold nuclear matter., Comment: 7 pages

Chiral anomaly modifies the scattering processes in chiral systems which can be computed using the Maxwell-Chern-Simons theory that couples electrodynamics to the pseudoscalar field $\theta$ describing the topological charge induced be external sources. Assuming slow variation of the topological charge density, the fermion scattering cross section is computed in the Born approximation and is found to have a resonance at the scattering angles proportional to the chiral conductivity. As a result, the transport coefficients are suppressed at high temperatures. The anisotropy of the cross section arises due to the spatial variation of the topological charge; its effect on the electrical conductivity is discussed., Comment: 14 pages, v2: improved presentation, the role of the chiral instability discussed, typos fixed

We investigate the scattering of a quark on a heavy nucleus at high energies using the time-dependent basis light-front quantization (tBLFQ) formalism, which is the first application of the tBLFQ formalism in QCD. We present the real-time evolution of the quark wave function in a strong classical color field of the relativistic nucleus, described as the Color Glass Condensate. The quark and the nucleus color field are simulated in the QCD SU(3) color space. We calculate the total and the differential cross sections, and the quark distribution in coordinate and color spaces using the tBLFQ approach. We recover the eikonal cross sections in the eikonal limit. We find that the differential cross section from the tBLFQ simulation is in agreement with a perturbative calculation at large $p_\perp$, and it deviates from the perturbative calculation at small $p_\perp$ due to higher-order contributions. In particular, we relax the eikonal limit by letting the quark carry realistic finite longitudinal momenta. We study the sub-eikonal effect on the quark through the transverse coordinate distribution of the quark with different longitudinal momentum, and we find the sub-eikonal effect to be sizable. Our results can significantly reduce the theoretical uncertainties in small $p_\perp$ region which has important implications to the phenomenology of the hadron-nucleus and deep inelastic scattering at high energies.

Electromagnetic field of a fast electric charge in nuclear matter with spatially uniform but random topological charge density is derived. A useful approximation is developed for the relativistic heavy-ion collisions., Comment: 12 pages, 4 figures; V2: a few minor changes + typos

The time-evolution of the magnetic field in hot homogeneous nuclear matter has two qualitatively different stages separated by the sphaleron transition time $\tau_c$. At early times the axial chemical potential and the corresponding chiral conductivity $\sigma_\chi$ are slow functions of time. The soft chiral modes $k<\sigma_\chi$ of the magnetic field grow exponentially with time, which is known as the chiral instability. At later times $\sigma_\chi$ fluctuates due to the sphaleron transitions and can be regarded as a random process. It is argued that the average magnetic field is exponentially damped at later times. The time-evolution of the average magnetic energy is more complicated and depends on the electrical conductivity of the chiral matter but does not depend on chirality. It exhibits instability only if the matter is a poor electrical conductor, such as the quark-gluon plasma near the critical temperature. The precise conditions for the instability and the growth rate of the unstable modes are derived., Comment: 17 pages, 1 figure; v2: discussion added and a few typos fixed

Domains of finite topological charge density can exist in chiral materials and chiral matter. Spatial and temporal variation of the average topological charge density, represented by the $\theta$-field, induces anomalous currents that are responsible for the chiral magnetic effect, the anomalous Hall effect and other phenomena that are intimately related to the chiral anomaly. We consider domains with constant average topological charge density. We argue that even though the Maxwell equations in the bulk are not altered, the chiral anomaly manifests itself by the way of the boundary conditions. This is illustrated by several examples. The first example deals with the refraction of plane electromagnetic wave on a surface of a constant-$\theta$ domain. We derive the modified Fresnel equations and discuss the effect of the chiral anomaly on the amplitude and polarization of the reflected and transmitted waves. In particular, we argue that the Brewster's angle is sensitive to the value of $\theta$. In the second example we compute the spectrum of the transition radiation at high frequencies and show that it is enhanced at finite $\theta$., Comment: 13 pages, 4 figures

A new mechanism of photon emission in the quark-gluon plasma is proposed. Photon dispersion relation in the presence of the $CP$-odd topological regions generated by the chiral anomaly acquires an imaginary mass. It allows photon radiation through the decay $q\to q\gamma$ and annihilation $q\bar q\to \gamma$ processes closely related to the chiral Cherenkov radiation. Unlike previous proposals this mechanism does not require an external magnetic field. The differential photon emission rate per unit volume is computed and shown to be comparable to the rate of photon emission in conventional processes., Comment: 12 pages, 1 figure

We study exclusive charmonium and bottomonium production in ultra-peripheral heavy-ion collisions and electron-ion collisions within the dipole picture. We employ heavy quarkonium light-front wavefunctions obtained within the basis light-front quantization framework, which has some features of the light-front holographic QCD. We focus on comparison with measurements of exclusive charmonium and bottomonium production in ultraperipheral $pp$, $p$Pb and PbPb collisions at LHC and find reasonable agreement with the cross sections. We also discuss the coherent production cross-section ratios of excited states to the ground state for charmonium and bottomonium, which exhibit insensitivity to the dipole model parameters. We show that electron-ion collisions provide an opportunity for a quantitative study of heavy quarkonium structure., Comment: 10 pages, 5 figures

A significant contribution to the electromagnetic radiation by a fast electric charge moving in anisotropic chiral matter arises from spontaneous photon radiation due to the chiral anomaly. While such a process, also known as the "vacuum Cherenkov radiation", is forbidden in the QED vacuum, it can occur in chiral matter, where it is more appropriate to call it the "chiral Cherenkov radiation". Its contribution to the radiation spectrum is of order $\alpha^2$ compared to $\alpha^3$ of the bremsstrahlung. I derive the frequency spectrum and the angular distribution of this radiation in the high energy limit. The quantum effects due to the hard photon emission and the fermion mass are taken into account. The obtained spectra are analyzed in the case the quark-gluon plasma and a Weyl semimetal., Comment: 13 pages, 6 figures

A fast charged particle crossing the boundary between the chiral matter and vacuum radiates the transition radiation. Its most remarkable features --- the resonant behavior at a certain emission angle and the circular polarization of the spectrum --- depend on the parameters of the chiral anomaly in a particular material/matter. The chiral transition radiation can be used to investigate the chiral anomaly in such diverse media as the quark-gluon plasma, the Weyl semimetals, and the axionic dark matter., Comment: 6 pages; v2: typo fixed, discussion added

Modification of the photon dispersion relation in chiral matter enables $1\to 2$ scattering. As a result, the single fermion and photon states are unstable to photon radiation and pair production respectively. In particular, a fast fermion moving through chiral matter can spontaneously radiate a photon, while a photon can spontaneously radiate a fast fermion and anti-fermion pair. The corresponding spectra are derived in the ultra-relativistic approximation. It is shown that the polarization of the produced and decayed photons is determined by the sign of the chiral conductivity. Impact of a flat thin domain wall on the spectra is computed., Comment: 13 pages. v2: error in IVA corrected, explanations and references added, typos fixed

We survey recent progress in calculating properties of the electron and hadrons within the Basis Light Front Quantization (BLFQ) approach. We include applications to electromagnetic and strong scattering processes in relativistic heavy ion collisions. We present an initial investigation into the glueball states by applying BLFQ with multigluon sectors, introducing future research possibilities on multi-quark and multi-gluon systems., Comment: Presented at LightCone 2017, Mumbai, India

The Chiral Magnetic Effect (CME) -- the separation of positive and negative electric charges along the direction of the external magnetic field in quark-gluon plasma and other topologically non-trivial media -- is a consequence of the coupling of electrodynamics to the topological gluon field fluctuations that form metastable $CP$-odd domains. In phenomenological models it is usually assumed that the domains are uniform and the influence of the domain walls on the electric current flow is not essential. This paper challenges the latter assumption. A simple model consisting of a uniform spherical domain in a uniform time-dependent magnetic field is introduced and analytically solved. It is shown that (i) no electric current flows into or out of the domain, (ii) the charge separation current, viz. the total electric current flowing inside the domain in the external field direction, is a dissipative Ohm current, (iii) the CME effect can be produced either by the anomalous current or by the boundary conditions on the domain wall and (iv) the charge separation current oscillates in plasma long after the external field decays. These properties are qualitatively different from the CME in an infinite medium., Comment: 16 pages, 6 figures

Intense electromagnetic fields are created in the quark-gluon plasma by the external ultra-relativistic valence charges. The time-evolution and the strength of this field are strongly affected by the electrical conductivity of the plasma. Yet, it has recently been observed that the effect of the magnetic field on the plasma flow is small. We compute the effect of plasma flow on magnetic field and demonstrate that it is less than 10\%. These observations indicate that the plasma hydrodynamics and the dynamics of electromagnetic field decouple. Thus, it is a very good approximation, on the one hand, to study QGP in the background electromagnetic field generated by external sources and, on the other hand, to investigate the dynamics of magnetic field in the background plasma. We also argue that the wake induced by the magnetic field in plasma is negligible., Comment: 16 pages, 5 figures

We study the electrodynamics of a chiral medium with electric and magnetic charges using the effective Maxwell-Chern-Simons theory extended to include the magnetic current. The exchange of helicity between the chiral medium and the magnetic field, known as the inverse cascade, is controlled by the chiral anomaly equation. In the presence of the magnetic current, the magnetic helicity is dissipated, so that the inverse cascade stops when the magnetic helicity vanishes while the chiral conductivity reaches a non-vanishing stationary value satisfying $\sigma_\chi^2< 4\sigma_e\sigma_m$, where $\sigma_e$, $\sigma_m$ and $\sigma_\chi$ are the electric, magnetic and chiral conductivities respectively. We argue that this state is superconducting and exhibits the Meissner effect for both electric and magnetic fields. Moreover, this state is stable with respect to small magnetic helicity fluctuations; the magnetic helicity becomes unstable only when the inequality mentioned above is violated., Comment: 13 pages, 11 figures. To appear in Phys. Lett. B

We compute the electromagnetic field created by an ultrarelativistic charged particle in vacuum at distances comparable to the particle Compton wavelength. The wave function of the particle is governed by the Klein-Gordon equation, for a scalar particle, or the Dirac equation, for a spin-half particle. The produced electromagnetic field is essentially different in magnitude and direction from the Coulomb field, induced by a classical point charge, due to the quantum diffusion effect. Thus, a realistic computation of the electromagnetic field produced in heavy-ion collisions must be based upon the full quantum treatment of the valence quarks., Comment: 4 pages, 4 figures, Proceedings of the XXVI International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2017)

We compute electromagnetic fields created by a relativistic charged spin-half particle in empty space at distances comparable to the particle Compton wavelength. The particle is described as a wave packet evolving according to the Dirac equation. It produces the electromagnetic field that is essentially different from the Coulomb field due to the quantum diffusion effect., Comment: 10 pages, 10 figures

Magnetic field is unstable in a medium with time-independent chiral conductivity. Owing to the chiral anomaly, the electromagnetic field and the medium exchange helicity which results in time-evolution of the chiral conductivity. Using the fastest growing momentum and helicity state of the vector potential as an ansatz, the time-evolution of the chiral conductivity and magnetic field is solved analytically. The solution for the hot and cold equations of state shows that the magnetic field does not develop an instability due to he helicity conservation. Moreover, it develops a peak only if a significant part of the \emph{initial} helicity is stored in the medium. The initial helicity determines the height and position of the peak., Comment: 16 pages, 8 figures; v2-4: many references, discussions and one figure added

We study the real-time evolution of an electron influenced by intense electromagnetic fields using the time-dependent basis light-front quantization (tBLFQ) framework. We focus on demonstrating the non-perturbative feature of the tBLFQ approach through a realistic application of the strong coupling QED problem, in which the electromagnetic fields are generated by an ultra-relativistic nucleus. We calculate transitions of an electron influenced by such electromagnetic fields and we show agreement with light-front perturbation theory when the atomic number of the nucleus is small. We compare tBLFQ simulations with perturbative calculations for nuclei with different atomic numbers, and obtain the significant higher-order contributions for heavy nuclei. The simulated real-time evolution of the momentum distribution of an electron evolving inside the strong electromagnetic fields exhibits significant non-perturbative corrections comparing to light-front perturbation theory calculations. The formalism used in this investigation can be extended to QCD problems in heavy ion collisions and electron ion collisions., Comment: 13 pages, 6 figures

We study exclusive charmonium production in diffractive deep inelastic scattering and ultra-peripheral heavy-ion collisions within the dipole picture. The mass spectrum and light-front wavefunctions of charmonium are obtained from the basis light-front quantization approach, using the one-gluon exchange interaction plus a confining potential inspired by light-front holography. We apply these light-front wavefunctions to exclusive charmonium production. The resulting cross sections are in reasonable agreement with electron-proton collision data at HERA and ultra-peripheral nucleus collision measurements at RHIC and LHC. The charmonium cross-section has model dependence on the dipole model. We observe that the cross-section ratio of excited states to the ground state has a weaker dependence than the cross-section itself. We suggest that measurements of excited states of heavy quarkonium production in future electron-ion collision experiments will impose rigorous constraints on heavy quarkonium light-front wavefunctions, thus improving our understanding of meson structure, which eventually will help us develop a precise description of the gluon distribution function in the small-$x$ regime., Comment: 4 pages, 4 figures, proceeding prepared for Hard Probes 2016

Quantitative calculations of the properties of hadrons and nuclei, with assessed uncertainties, have emerged as competitive with experimental measurements in a number of major cases. We may well be entering an era where theoretical predictions are critical for experimental progress. Cross-fertilization between the fields of relativistic hadronic structure and non-relativistic nuclear structure is readily apparent. Non-perturbative renormalization methods such as Similarity Renormalization Group and Okubo-Lee-Suzuki schemes as well as many-body methods such as Coupled Cluster, Configuration Interaction and Lattice Simulation methods are now employed and advancing in both major areas of physics. New algorithms to apply these approaches on supercomputers are shared among these areas of physics. The roads to success have intertwined with each community taking the lead at various times in the recent past. I briefly sketch these fascinating paths and comment on some symbiotic relationships. I also overview some recent results from the Hamiltonian Basis Light-Front Quantization approach., Comment: 11 pages, 8 figures, LC2016 conference paper submitted to Few Body Systems

Using the charmonium light-front wavefunctions obtained by diagonalizing an effective Hamiltonian with the one-gluon exchange interaction and a confining potential inspired by light-front holography in the basis light-front quantization formalism, we compute production of charmonium states in diffractive deep inelastic scattering and ultra-peripheral heavy ion collisions within the dipole picture. Our method allows us to predict yields of all vector charmonium states below the open flavor thresholds in high-energy deep inelastic scattering, proton-nucleus and ultra-peripheral heavy ion collisions, without introducing any new parameters in the light-front wavefunctions. The obtained charmonium cross section is in reasonable agreement with experimental data at HERA, RHIC and LHC. We observe that the cross-section ratio $\sigma_{\Psi(2s)}/\sigma_{J/\Psi}$ reveals significant independence of model parameters., Comment: 12 pages, 5 figures

Metastable CP-odd domains of the hot QCD matter are coupled to QED via the chiral anomaly. The topology of electromagnetic field in these domains is characterized by magnetic helicity. It is argued, using the Maxwell-Chern-Simons model, that spatial inhomogeneity of the domains induces spontaneous transitions of electromagnetic field between the opposite magnetic helicity states., Comment: 10 pages

Electromagnetic fields are generated in high energy nuclear collisions by spectator valence protons. These fields are traditionally computed by integrating the Maxwell equations with point sources. One might expect that such an approach is valid at distances much larger than the proton size and thus such a classical approach should work well for almost the entire interaction region in the case of heavy nuclei. We argue that, in fact, the contrary is true: due to the quantum diffusion of the proton wave function, the classical approximation breaks down at distances of the order of the system size. We compute the electromagnetic field created by a charged particle described initially as a Gaussian wave packet of width 1 fm and evolving in vacuum according to the Klein-Gordon equation. We completely neglect the medium effects. We show that the dynamics, magnitude and even sign of the electromagnetic field created by classical and quantum sources are different., Comment: 12 pages, 4 figures. V2: a numerical error corrected, figures improved, other minor improvements

A quark propagating through the quark gluon plasma and scattering off the thermal gluons can radiate photons in states with definite angular momentum and magnetic helicity. These states, known as the Chandrasekhar-Kendall states, are eigenstates of the curl operator and have a non-trivial topology. I compute spectrum of these states in the ultrarelativistic limit and study its properties., Comment: 15 pages, V3: typos fixed, one appendix and one figure added

When quark-gluon plasma emerges in the wake of a heavy-ion collision, magnetic field created by the valence charges has already permitted the entire interaction region. Evolution of this "initial" field in plasma is governed by Maxwell equations in electrically conducting medium. As the plasma expands external valence charges induce magnetic field that also contributes to the total magnetic field in plasma. We solve the initial value problem describing these processes and argue that the initial magnetic field often dominates over the one induced by the valence charges. In particular, it grows approximately proportional to the collision energy, unlike the induced component, which is energy-independent. As a result, magnetic field has a significant phenomenological influence on quark-gluon plasma at the LHC energies over its entire lifetime., Comment: 13 pages

An essential part of experimental program at the future Electron Ion Collider is the study of the nuclear structure and dynamics at low $x$. DIS at low $x$ is characterized by large longitudinal coherence length that by far exceeds radii of heavy nuclei. The coherent behavior is essential feature of the nuclear matter at low $x$. This pertains not only to the strong interactions, but also to electromagnetic ones. Coherent interactions of a projectile with nucleons in a heavy nucleus are characterized by parameters $\alpha_s^2 A^{1/3}\sim 1$ and $\alpha Z\sim 1 $ in strong and electromagnetic interactions respectively. Contributions exhibiting non-trivial dependence on $\alpha Z$ are called the Coulomb corrections. We compute the Coulomb corrections to the cross sections of the semi-inclusive and diffractive DIS. We show that they violate the geometric scaling in a wide range of photon virtualities and is weakly $x$-independent. In heavy nuclei at low $Q^2$ the Coulomb correction to the total and diffractive cross sections is about 20% and 40% correspondingly., Comment: Contribution to the proceedings of DIS2015

Time evolution of electromagnetic field created in heavy-ion collisions strongly depends on the electromagnetic response of the quark-gluon plasma, which can be described by the Ohmic and chiral conductivities. The later is intimately related to the Chiral Magnetic Effect. I argue that a solution to the classical Maxwell equations at finite chiral conductivity is unstable due to the soft modes $k<\sigma_\chi$ that grow exponentially with time. In the kinematical region relevant for the relativistic heavy-ion collisions, I derive analytical expressions for the magnetic field of a point charge. I show that finite chiral conductivity causes oscillations of magnetic field at early times., Comment: 13 pages, 3 figures; v2: improved presentation, typos fixed, v3: a mistake in Eq. (62) is fixed

Magnetic fields produced in collisions of electrically charged particles at relativistic energies are strong enough to affect the dynamics of the strong interactions. In particular, it induces radiation of vector bosons by relativistic fermions. To develop deeper insight into this problem, I calculate the corresponding spectrum in constant magnetic field and analyze its angular distribution and mass dependence. As an application, I consider synchrotron radiation of virtual photon by the quark-gluon plasma., Comment: 13 pages, 6 figures, V2: a couple of errors fixed

Synchrotron photon spectrum in heavy-ion collisions is computed taking into account the spatial and temporal structure of magnetic field. It is found that a significant fraction of photon excess in heavy-ion collisions in the region $k_\bot=1-3$GeV can be attributed to the synchrotron radiation. Azimuthal anisotropy of the synchrotron photon spectrum is characterized by the Fourier coefficients $v_2=4/7$ and $v_4=1/10$ that are independent of photon momentum and centrality., Comment: 9 pages, 3 figures

I compute the Coulomb correction to the total and diffractive cross sections for virtual photon scattering off a heavy nucleus at low $x$. I show that it violates the geometric scaling in a wide range of photon virtualities and is weakly $x$-independent. In heavy nuclei at low $Q^2$ the Coulomb correction to the total and diffractive cross sections is about 20% and 40% correspondingly., Comment: 4 pages, 4 figures