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Dmitri E. Kharzeev

Publications and source records attributed to Dmitri E. Kharzeev.

At least 37 records · Page 2Linked to original sources
arXiv2024

Real-time chiral dynamics at finite temperature from quantum simulation

In this study, we explore the real-time dynamics of the chiral magnetic effect (CME) at a finite temperature in the (1+1)-dimensional QED, the massive Schwinger model. By introducing a chiral chemical potential $μ_5$ through a quench process, we drive the system out of equilibrium and analyze the induced vector currents and their evolution over time. The Hamiltonian is modified to include the time-dependent chiral chemical potential, thus allowing the investigation of the CME within a quantum computing framework. We employ the quantum imaginary time evolution (QITE) algorithm to study the thermal states, and utilize the Suzuki-Trotter decomposition for the real-time evolution. This study provides insights into the quantum simulation capabilities for modeling the CME and offers a pathway for studying chiral dynamics in low-dimensional quantum field theories.

hep-ph↗
arXiv2024

Chiral Magnetic Effect in Heavy Ion Collisions: The Present and Future

The chiral magnetic effect (CME) is a collective quantum phenomenon that arises from the interplay between gauge field topology and fermion chiral anomaly, encompassing a wide range of physical systems from semimetals to quark-gluon plasma. This review, with a focus on CME and related effects in heavy ion collisions, aims to provide an introductory discussion on its conceptual foundation and measurement methodology, a timely update on the present status in terms of experimental findings and theoretical progress, as well as an outlook into the open problems and future developments.

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arXiv2024

Temporal Entanglement Entropy as a probe of Renormalization Group Flow

The recently introduced concept of timelike entanglement entropy has sparked a lot of interest. Unlike the traditional spacelike entanglement entropy, timelike entanglement entropy involves tracing over a timelike subsystem. In this work, we propose an extension of timelike entanglement entropy to Euclidean space ("temporal entanglement entropy"), and relate it to the renormalization group (RG) flow. Specifically, we show that tracing over a period of Euclidean time corresponds to coarse-graining the system and can be connected to momentum space entanglement. We employ Holography, a framework naturally embedding RG flow, to illustrate our proposal. Within cutoff holography, we establish a direct link between the UV cutoff and the smallest resolvable time interval within the effective theory through the irrelevant $T\bar T$ deformation. Increasing the UV cutoff results in an enhanced capability to resolve finer time intervals, while reducing it has the opposite effect. Moreover, we show that tracing over a larger Euclidean time interval is formally equivalent to integrating out more UV degrees of freedom (or lowering the temperature). As an application, we point out that the temporal entanglement entropy can detect the critical Lifshitz exponent $z$ in non-relativistic theories which is not accessible from spatial entanglement at zero temperature and density.

hep-th↗
arXiv2024

Quantum simulation of entanglement and hadronization in jet production: lessons from the massive Schwinger model

The possible link between entanglement and thermalization, and the dynamics of hadronization are addressed by studying the real-time response of the massive Schwinger model coupled to external sources. This setup mimics the production and fragmentation of quark jets, as the Schwinger model and QCD share the properties of confinement and chiral symmetry breaking. By using quantum simulations on classical hardware, we study the entanglement between the produced jets, and observe the growth of the corresponding entanglement entropy in time. This growth arises from the increased number of contributing eigenstates of the reduced density matrix with sufficiently large and close eigenvalues. We also investigate the physical nature of these eigenstates, and find that at early times they correspond to fermionic Fock states. We then observe the transition from these fermionic Fock states to meson-like bound states as a function of time. In other words, we observe how hadronization develops in real time. At late times, the local observables at mid-rapidity (such as the fermion density and the electric field) approach approximately constant values, suggesting the onset of equilibrium and approach to thermalization.

hep-ph↗
arXiv2024

Detecting anomalous CP violation in heavy ion collisions through baryon-electric charge correlations

The chiral magnetic effect (CME) and the chiral vortical effect (CVE) induce a correlation between baryon and electric currents. We show that this correlation can be detected using a new observable: a mixed baryon-electric charge correlator. This correlator is proportional to the baryon asymmetry, suggesting a novel way to separate the chiral effects from the background in heavy ion collisions.

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arXiv2024

Entanglement in massive Schwinger model at finite temperature and density

We evaluate the entanglement entropy and entropic function of massive two dimensional QED (Schwinger model) at finite temperature, density, and $θ$-angle. In the strong coupling regime, the entropic function is dominated by the boson mass for large spatial intervals, and reduces to the CFT result for small spatial intervals. We also discuss the entanglement spectrum at finite temperature and a finite $θ$-angle.

hep-th↗
arXiv2024

Probing the onset of maximal entanglement inside the proton in diffractive DIS

It has been proposed that at small Bjorken $x$, or equivalently at high energy, hadrons represent maximally entangled states of quarks and gluons. This conjecture is in accord with experimental data from the electron-proton collider HERA at the smallest accessible $x$. In this Letter, we propose to study the onset of the maximal entanglement inside the proton using Diffractive Deep Inelastic Scattering. It is shown that the data collected by the H1 Collaboration at HERA allows to probe the transition to the maximal entanglement regime. By relating the entanglement entropy to the entropy of final state hadrons, we find a good agreement with the H1 data using both the exact entropy formula as well as its asymptotic expansion which indicates the presence of a nearly maximally-entangled state. Finally, future opportunities at the Electron Ion Collider are discussed.

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arXiv2023

Signatures of baryon junctions in semi-inclusive deep inelastic scattering

Local gauge invariance of the baryon wave function leads to the emergence of a baryon junction, where three (or $N$, in $SU(N)$ gauge theory) string operators merge. The existence of baryon junction dramatically affects the dynamics of baryon stopping at high energies, and the corresponding predictions are supported by the recent data from STAR Collaboration at the Relativistic Heavy Ion Collider. Here we outline the ways in which the baryon junctions can be tested in semi-inclusive deep inelasttic scattering at Jefferson Laboratory and the future Electron Ion Collider.

hep-ph↗
arXiv2023

Spacetime dynamics of chiral magnetic currents in a hot non-Abelian plasma

The correlations of electric currents in hot non-Abelian plasma are responsible for the experimental manifestations of the chiral magnetic effect (CME) in heavy-ion collisions. We evaluate these correlations using holography, and show that they are driven by large-scale topological fluctuations. In a non-Abelian plasma with chiral fermions, local axial charge can be generated either by topological fluctuations (creating domains with nonzero Chern-Simons number) or by thermal fluctuations. Within holography, we investigate the dynamical creation of the axial charge and isolate the imprint of the topological dynamics on the spatial correlations of electric current. In particular, we show that the spatial extent of the current correlation is quite large ($\sim 1\ {\rm fm}$) and grows with time, which is consistent with sphaleronlike dynamics. We provide numerical estimates for this spatial size that can be used as an input in phenomenological analyses.

hep-ph↗
arXiv2023

Entanglement entropy in a time-dependent holographic Schwinger pair creation

We analyze the entanglement of a Schwinger pair created by a time-dependent pulse. In the semi-classical approximation, the pair creation by a pulse of external electric field is captured by a periodic worldline instanton. At strong gauge coupling, the gauge-gravity dual worldsheet instanton exhibits a falling wormhole in AdS. We identify the tunneling time at the boundary with the inverse Unruh temperature, and derive the pertinent entanglement entropy between the created pair using thermodynamics. The entanglement entropy is enhanced by the sub-barrier tunneling process, and partly depleted by the radiation in the post-barrier process.

hep-th↗
arXiv2023

Chiral catalysis of nuclear fusion in molecules

At low energies, nuclear fusion is strongly affected by electron screening of the Coulomb repulsion among the fusing nuclei. It may thus be possible to catalyze nuclear fusion in molecules (i.e., to fuse specific nuclei in situ) through quantum control of electron wave functions in intense laser fields. The circularly polarized (chiral) laser field can effectively squeeze the electron wave functions, greatly enhancing the screening in the spatial region relevant for the fusion process. We estimate the corresponding fusion probabilities, and find that the proposed chiral catalysis of nuclear fusion in molecules may be observable, potentially with important practical applications.

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arXiv2023

Entanglement in a holographic Schwinger pair with confinement

We revisit the entanglement of a Schwinger pair created by external fields of arbitrary strength, using a holographic dual description of QCD. When external fields are strong in comparison to the string tension, the entanglement is geometrically tied to the Einstein-Rosen (ER) bridge in the bulk, and disappears when the pair production is not exponentially suppressed at the boundary. For moderate external fields, the entanglement is shown to follow from the geometrical interplay between the position of the ER bridge and the confining wall in the bulk. We clarify the physical nature of quantum entanglement in pair production, and connect it to the entropy of entanglement between the left- and right-moving fermions. In particular, we clarify the effect of real radiation off the produced particles on quantum entanglement of the pair.

hep-th↗
arXiv2023

Non-linear chiral magnetic waves

The chiral magnetic wave (CMW) is a macroscopic quantum phenomenon that arises due to the mixing of the electric and chiral charge oscillations induced by the chiral anomaly. In this study we report the first quantum simulation (on classical hardware) of the real-time dynamics of CMWs in Schwinger model. Our quench protocol is the following: at $t=0$ we suddenly place an electric dipole at the middle of our lattice. Due to chiral anomaly, this dipole excites the CMW that propagates towards the edges of the lattice. In Schwinger model tuned to the conformal critical point (at $θ= π$, $m/g \simeq 0.2$), we find a gapless linear CMW that propagates with the speed of light. For massless Schwinger model ($θ=0, m=0$), we find a gapped linear CMW, in accord with previous analytical analyses. For massive Schwinger model (that is dual to strongly interacting bosonic theory), we enter the new regime of nonlinear CMWs, where we find a surprise. Specifically, for $m/g > 1$, the frequency of electric charge oscillations becomes much smaller than the frequency of the oscillations of the chiral charge. For $m/g =4$, we find a solution corresponding to a nearly static electric dipole with fast oscillations of the chiral charge confined within. We call this solution a "thumper" and study its properties in detail.

hep-ph↗
arXiv2023

Detecting the critical point through entanglement in Schwinger model

Using quantum simulations on classical hardware, we study the phase diagram of the massive Schwinger model with a $θ$-term at finite chemical potential $μ$. We find that the quantum critical point in the phase diagram of the model can be detected through the entanglement entropy and entanglement spectrum. As a first step, we chart the phase diagram using conventional methods by computing the dependence of the charge and chiral condensates on the fermion mass $m$, coupling constant $g$, and the chemical potential $μ$. At zero density, the Schwinger model possesses a quantum critical point at $θ=π$ and $m/g \simeq 0.33$. We find that the position of this quantum critical point depends on the chemical potential. Near this quantum critical point, we observe a sharp maximum in the entanglement entropy. Moreover, we find that the quantum critical point can be located from the entanglement spectrum by detecting the position of the gap closing point.

hep-ph↗
arXiv2022

Chirality distributions inside baryons in ${\rm QCD_2}$

The connection between the spin distribution and the topological structure of the baryon is an open and important problem. Here we address it using QCD in $(1+1)$ spacetime dimensions, which is exactly solvable at large number of colors $N$. It is found that the distribution of chirality inside a baryon is drastically different from a chirality distribution inside states with zero baryon number, ``mesons". This difference is shown to arise from the topological structure of the baryon -- at large $N$, all of the baryon's chirality is concentrated near $x=0$, whereas in a meson state it vanishes in the small $x$ limit. Our results illustrate how the constituent features of the baryon reemerge and are tied to the topological features of the bosonized solitonic solution. Possible implications for QCD in $(3+1)$ dimensions and for deep inelastic scattering experiments are discussed.

hep-ph↗
arXiv2022

Implications of the isobar run results for chiral magnetic effect in heavy ion collisions

Chiral magnetic effect (CME) is a macroscopic transport phenomenon induced by quantum anomaly in the presence of chiral imbalance and an external magnetic field. Relativistic heavy ion collisions provide the unique opportunity to look for CME in a non-Abelian plasma, where the chiral imbalance is created by topological transitions similar to those occurring in the Early Universe. The isobar run at Relativistic Heavy Ion Collider was proposed as a way to separate the possible CME signal driven by magnetic field from the background. The first blind analysis results from this important experiment have been recently released by the STAR Collaboration. Under the pre-defined assumption of identical background in RuRu and ZrZr, the results are inconsistent with the presence of CME, as well as with all existing theoretical models (whether including CME or not). However the observed difference of backgrounds must be taken into account before any physical conclusion is drawn. In this paper, we show that once the observed difference in hadron multiplicity and collective flow are quantitatively taken into account, the STAR results could be consistent with a finite CME signal contribution of about $(6.8\pm2.6)\%$.

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arXiv2022

Entropy Suppression through Quantum Interference in Electric Pulses

The Schwinger process in strong electric fields creates particles and antiparticles that are entangled. The entropy of entanglement between particles and antiparticles has been found to be equal to the statistical Gibbs entropy of the produced system. Here we study the effect of quantum interference in sequences of electric pulses, and show that quantum interference suppresses the entanglement entropy of the created quantum state. This is potentially relevant to quantum-enhanced classical communications. Our results can be extended to a wide variety of two-level quantum systems.

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