scholarly journals Vacuum instability in a constant inhomogeneous electric field: a new example of exact nonperturbative calculations

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
T. C. Adorno ◽  
S. P. Gavrilov ◽  
D. M. Gitman
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Transition Probabilities ◽  
Particle Creation ◽  
Field Configuration ◽  
Quantum Processes ◽  
Reflection And Transmission ◽  
Vacuum Instability ◽  
Klein Gordon

Abstract Basic quantum processes (such as particle creation, reflection, and transmission on the corresponding Klein steps) caused by inverse-square electric fields are calculated. These results represent a new example of exact nonperturbative calculations in the framework of QED. The inverse-square electric field is time-independent, inhomogeneous in the x -direction, and is inversely proportional to x squared. We find exact solutions of the Dirac and Klein–Gordon equations with such a field and construct corresponding in- and out-states. With the help of these states and using the techniques developed in the framework of QED with x-electric potential steps, we calculate characteristics of the vacuum instability, such as differential and total mean numbers of particles created from the vacuum and vacuum-to-vacuum transition probabilities. We study the vacuum instability for two particular backgrounds: for fields widely stretches over the x-axis (small-gradient configuration) and for the fields sharply concentrates near the origin $$x=0$$x=0 (sharp-gradient configuration). We compare exact results with ones calculated numerically. Finally, we consider the electric field configuration, composed by inverse-square fields and by an x-independent electric field between them to study the role of growing and decaying processes in the vacuum instability.

scholarly journals Exactly solvable cases in QED with t-electric potential steps

2017 ◽  
Vol 32 (18) ◽  
pp. 1750105 ◽  
Author(s):  
T. C. Adorno ◽  
S. P. Gavrilov ◽  
D. M. Gitman
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Electric Potential ◽  
Constant Electric Field ◽  
Particle Creation ◽  
External Electromagnetic Field ◽  
Mean Values ◽  
Closed Form Solutions ◽  
Exactly Solvable ◽  
Klein Gordon

In this paper, we present in detail consistent QED (and scalar QED) calculations of particle creation effects in external electromagnetic field that correspond to three most important exactly solvable cases of t-electric potential steps: Sauter-like electric field, T-constant electric field, and exponentially growing and decaying electric fields. In all these cases, we succeeded to obtain new results, such as calculations in the modified configurations of the above-mentioned steps and detailed considerations of new limiting cases in already studied steps. As was recently discovered by us, the information derived from considerations of exactly solvable cases allows one to make some general conclusions about quantum effects in fields for which no closed form solutions of the Dirac (or Klein–Gordon) equation are known. In the present paper, we briefly represent such conclusions about universal behavior of vacuum mean values in slowly varying strong electric fields.

scholarly journals Elucidating the Influence of Electric Fields toward CO2 Activation on YSZ (111)

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 271
Author(s):  
Nisa Ulumuddin ◽  
Fanglin Che ◽  
Jung-Il Yang ◽  
Su Ha ◽  
Jean-Sabin McEwen
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Heterogeneous Catalysts ◽  
Co2 Reduction ◽  
Total Density ◽  
Reverse Water Gas Shift ◽  
High Thermodynamic Stability ◽  
Shift Reaction ◽  
Water Gas

Despite its high thermodynamic stability, the presence of a negative electric field is known to facilitate the activation of CO2 through electrostatic effects. To utilize electric fields for a reverse water gas shift reaction, it is critical to elucidate the role of an electric field on a catalyst surface toward activating a CO2 molecule. We conduct a first-principles study to gain an atomic and electronic description of adsorbed CO2 on YSZ (111) surfaces when external electric fields of +1 V/Å, 0 V/Å, and −1 V/Å are applied. We find that the application of an external electric field generally destabilizes oxide bonds, where the direction of the field affects the location of the most favorable oxygen vacancy. The direction of the field also drastically impacts how CO2 adsorbs on the surface. CO2 is bound by physisorption when a +1 V/Å field is applied, a similar interaction as to how it is adsorbed in the absence of a field. This interaction changes to chemisorption when the surface is exposed to a −1 V/Å field value, resulting in the formation of a CO3− complex. The strong interaction is reflected through a direct charge transfer and an orbital splitting within the Olatticep-states. While CO2 remains physisorbed when a +1 V/Å field value is applied, our total density of states analysis indicates that a positive field pulls the charge away from the adsorbate, resulting in a shift of its bonding and antibonding peaks to higher energies, allowing a stronger interaction with YSZ (111). Ultimately, the effect of an electric field toward CO2 adsorption is not negligible, and there is potential in utilizing electric fields to favor the thermodynamics of CO2 reduction on heterogeneous catalysts.

scholarly journals Electric potential differences across auroral generator interfaces

2013 ◽  
Vol 31 (2) ◽  
pp. 251-261 ◽  
Author(s):  
J. De Keyser ◽  
M. Echim
Keyword(s):  
Electric Field ◽  
High Altitude ◽  
Electric Fields ◽  
Electric Potential ◽  
Equilibrium Configuration ◽  
Potential Difference ◽  
Field Profile ◽  
Electric Potential Difference ◽  
Electric Field Profile

Abstract. Strong localized high-altitude auroral electric fields, such as those observed by Cluster, are often associated with magnetospheric interfaces. The type of high-altitude electric field profile (monopolar, bipolar, or more complicated) depends on the properties of the plasmas on either side of the interface, as well as on the total electric potential difference across the structure. The present paper explores the role of this cross-field electric potential difference in the situation where the interface is a tangential discontinuity. A self-consistent Vlasov description is used to determine the equilibrium configuration for different values of the transverse potential difference. A major observation is that there exist limits to the potential difference, beyond which no equilibrium configuration of the interface can be sustained. It is further demonstrated how the plasma densities and temperatures affect the type of electric field profile in the transition, with monopolar electric fields appearing primarily when the temperature contrast is large. These findings strongly support the observed association of monopolar fields with the plasma sheet boundary. The role of shear flow tangent to the interface is also examined.

scholarly journals Can Electric Fields Drive Chemistry for an Aqueous Microdroplet?

2021 ◽  
Author(s):  
Hongxia Hao ◽  
Itai Leven ◽  
Teresa Head-Gordon
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Water Droplet ◽  
Reaction Rates ◽  
Surface Reactivity ◽  
Bulk Solution ◽  
Excess Charge ◽  
Electronic Effects ◽  
Rate Acceleration

Abstract Reaction rates of common organic reactions have been reported to increase by one to six orders of magnitude in aqueous microdroplets compared to bulk solution, but the reasons for the rate acceleration are poorly understood. We investigate the role of electric fields at water droplet surfaces that might explain the promotion of unusual reactive chemistry, along with changes in electric field profiles as a function of excess charge to model the electrospray fragmentation process. We find that electric field alignments along free O-H bonds at the surface yield field strength distributions that are ~30 MV/cm larger on average than that found for O-H bonds in the interior of the water droplet, consistent with greater surface reactivity. We emphasize the importance of both nuclear and electronic effects at the surface, and the non-linear coupling of intramolecular solute polarization with intermolecular solvent modes, as a necessary feature for predicting the higher field strengths at water droplet surfaces.

SPECTROSCOPY OF THE HYDROGEN AND ANTI-HYDROGEN ATOMS IN EXTERNAL FIELDS

2004 ◽  
Vol 18 (30) ◽  
pp. 3875-3886 ◽  
Author(s):  
LEONTI LABZOWSKY ◽  
VASILY SHARIPOV ◽  
DMITRI SOLOVYEV ◽  
GÜNTER PLUNIEN ◽  
GERHARD SOFF
Keyword(s):  
Magnetic Fields ◽  
Electric Field ◽  
External Electric Field ◽  
Electric Fields ◽  
Transition Probabilities ◽  
Cpt Violation ◽  
Hydrogen Atoms ◽  
Frequency Distributions ◽  
Electric And Magnetic Fields ◽  
Lorentz Line

The spectroscopical properties of hydrogen (H) and anti-hydrogen [Formula: see text] atoms in external electric and magnetic fields are discussed. This problem became important in connection with the recent experimental success in production of [Formula: see text] atoms. The main features of these experiments are briefly reviewed. The proposals for the search of the CPT violation via comparison of the H and [Formula: see text] spectra are shortly discussed. The spectroscopical differences between H and [Formula: see text] atoms in external magnetic fields and in parallel magnetic and electric fields are described in detail. It is proven that the positions of the maxima of the frequency distributions for transition probabilities in external electric field for H and [Formula: see text] atoms will deviate if the non-resonant corrections to the Lorentz line profile are taken into account.

FIRST-PRINCIPLES STUDY ON ELECTRIC-FIELD-INDUCED STATES OF SILICON MICROCLUSTERS

1996 ◽  
Vol 03 (01) ◽  
pp. 389-393 ◽  
Author(s):  
KAZUYUKI WATANABE ◽  
TAKASHI ABE ◽  
TSUYOSHI OGINO ◽  
SAKURA TAKEDA
Keyword(s):  
Electric Field ◽  
Bond Length ◽  
Electric Fields ◽  
First Principles ◽  
Bending Mode ◽  
Bond Stretching ◽  
Bond Bending ◽  
Cohesive Energies ◽  
Present Simulation

The first-principles molecular dynamics (FPMD) method is applied to a Si dimer and a Si trimer in electrostatic fields to calculate the charge polarization, the stable structures, and the cohesive energies. It is found that the bond length of the dimer increases, and the bond length and the bond angle of the trimer decrease as the electric field increases. The obtained structural change due to electric fields is compatible with the change in the cohesive energy. The vibrational dynamics of the dimer and trimer are also studied. The bond-bending mode of the trimer is found to be more largely influenced by the electric field than the bond-stretching mode. The present simulation revealed a fundamental role of electric fields in manipulating microclusters.

scholarly journals Role of inductive electric fields and currents in dynamical ionospheric situations

2007 ◽  
Vol 25 (2) ◽  
pp. 437-455 ◽  
Author(s):  
H. Vanhamäki ◽  
O. Amm ◽  
A. Viljanen
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Temporal Variations ◽  
Ionospheric Currents ◽  
Calculation Technique ◽  
Induced Field ◽  
Ionospheric Electric Field ◽  
Electric Fields And Currents ◽  
Current Systems

Abstract. We study the role of ionospheric induction in different commonly observed ionospheric situations. These include an intensifying electrojet, westward travelling surge (WTS) and Ω-band. We use data based, realistic models for these phenomena and calculate the inductive electric fields that are created due to the temporal variations of ionospheric currents. The ionospheric induction problem is solved using a new calculation technique that can handle non-uniform, time-dependent conductances and electric fields of any geometry. We find that in some situations inductive effects are not negligible and the ionospheric electric field is not a pure potential field, but has a significant induced rotational part. In the WTS and Ω-band models the induced electric field is concentrated in a small area, where the time derivatives are largest. In the electrojet model the induced field is significant over a large part of the jet area. In these examples the induced electric field has typical values of few mV/m, which amounts to several tens of percents of the potential electric field present at the same locations. The induced electric field is associated with ionospheric and field aligned currents (FAC), that modify the overall structure of the current systems. Especially the induced FAC are often comparable to the non-inductive FAC, and may thus modify the coupling between the ionosphere and magnetosphere in the most dynamical situations. We also present some examples with very simple ionospheric current systems, where the effect of different ionospheric parameters on the induction process is studied.

scholarly journals Asymptotic expansion of pair production probability in a time-dependent electric field

2015 ◽  
Vol 30 (35) ◽  
pp. 1550210
Author(s):  
Takashi Arai
Keyword(s):  
Asymptotic Expansion ◽  
Electric Field ◽  
Electric Fields ◽  
Quantum Electrodynamics ◽  
Strong Field ◽  
Order Term ◽  
Constant Electric Field ◽  
Particle Creation ◽  
Single Pulse ◽  
Time Interval

We study particle creation in a single pulse of an electric field in scalar quantum electrodynamics. We investigate the parameter condition for the case where the dynamical pair creation and Schwinger mechanism respectively dominate. Then, an asymptotic expansion for the particle distribution in terms of the time interval of the applied electric field is derived. We compare our result with particle creation in a constant electric field with a finite-time interval. These results coincide in an extremely strong field, however they differ in general field strength. We interpret the reason of this difference as a nonperturbative effect of high-frequency photons in external electric fields. Moreover, we find that the next-to-leading-order term in our asymptotic expansion coincides with the derivative expansion of the effective action.

scholarly journals On the role of neutral flow in field-aligned currents

2018 ◽  
Vol 36 (1) ◽  
pp. 53-57 ◽  
Author(s):  
Anthony J. Mannucci ◽  
Olga P. Verkhoglyadova ◽  
Xing Meng ◽  
Ryan McGranaghan
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Rest Frame ◽  
Geomagnetic Storms ◽  
Electron Flow ◽  
Lower Ionosphere ◽  
Momentum Balance ◽  
Neutral Atmosphere ◽  
Magnetospheric Dynamics

Abstract. In this brief note we explore the role of the neutral atmosphere in magnetosphere–ionosphere coupling. We analyze momentum balance in the ion rest frame to form hypotheses regarding the role of neutral momentum in the lower ionosphere during geomagnetic storms. Neutral momentum that appears in the ion rest frame is likely the result of momentum imparted to ionospheric ions by solar wind flow and the resultant magnetospheric dynamics. The resulting ion-neutral collisions lead to the existence of an electric field. Horizontal electron flow balances the momentum supplied by this electric field. We suggest a possible role played by the neutral atmosphere in generating field-aligned currents due to local auroral heating. Our physical interpretation suggests that thermospheric neutral dynamics plays a complementary role to the high-latitude field-aligned currents and electric fields resulting from magnetospheric dynamics. Keywords. Ionosphere (ionosphere–magnetosphere interactions; polar ionosphere) – magnetospheric physics (magnetosphere–ionosphere interactions)

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