Scalar quantum field coupled to boundaries and to a background magnetic field

2001 ◽  
Vol 42 (12) ◽  
pp. 5499-5521
Author(s):  
A. A. Actor ◽  
I. Bender
Keyword(s):  
Magnetic Field ◽  
Quantum Field ◽  
Background Magnetic Field ◽  
Scalar Quantum

RADIATIVE EFFECTS IN A CONSTANT MAGNETIC FIELD USING THE QUANTUM MECHANICAL PATH-INTEGRAL

1994 ◽  
Vol 09 (23) ◽  
pp. 2167-2178 ◽  
Author(s):  
D.G.C. MCKEON ◽  
T.N. SHERRY
Keyword(s):  
Magnetic Field ◽  
Field Theory ◽  
Quantum Field Theory ◽  
Path Integral ◽  
Constant Magnetic Field ◽  
Quantum Mechanical ◽  
Quantum Field ◽  
Matrix Elements ◽  
Loop Momentum ◽  
Background Magnetic Field

It has been shown how evaluation of matrix elements of the form <x| exp −iHt|y> using the quantum mechanical path-integral allows one to determine radiative corrections in quantum field theory without encountering loop momentum integrals. In this paper we show how this technique can be applied when there is a constant background magnetic field contributing to the “Hamiltonian” H.

scholarly journals Thermal Casimir effect with general boundary conditions

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
J. M. Muñoz-Castañeda ◽  
L. Santamaría-Sanz ◽  
M. Donaire ◽  
M. Tello-Fraile
Keyword(s):  
Boundary Conditions ◽  
Vacuum Energy ◽  
Casimir Effect ◽  
Quantum Field ◽  
Quantum Vacuum ◽  
Parallel Plates ◽  
Casimir Forces ◽  
Thermal Correction ◽  
Frequency Independent ◽  
Scalar Quantum

Abstract In this paper we study the system of a scalar quantum field confined between two plane, isotropic, and homogeneous parallel plates at thermal equilibrium. We represent the plates by the most general lossless and frequency-independent boundary conditions that satisfy the conditions of isotropy and homogeneity and are compatible with the unitarity of the quantum field theory. Under these conditions we compute the thermal correction to the quantum vacuum energy as a function of the temperature and the parameters encoding the boundary condition. The latter enables us to obtain similar results for the pressure between plates and the quantum thermal correction to the entropy. We find out that our system is thermodynamically stable for any boundary conditions, and we identify a critical temperature below which certain boundary conditions yield attractive, repulsive, and null Casimir forces.

Parametric excitation of magnetoacoustic waves by a pump magnetic field in a high-β plasma

1977 ◽  
Vol 17 (1) ◽  
pp. 93-103 ◽  
Author(s):  
N. F. Cramer
Keyword(s):  
Magnetic Field ◽  
Parametric Excitation ◽  
Acoustic Waves ◽  
Magnetic Pressure ◽  
Gas Pressure ◽  
Alfven Wave ◽  
Fast Wave ◽  
Magnetoacoustic Waves ◽  
Background Magnetic Field ◽  
The Waves

The parametric excitation of slow, intermediate (Alfvén) and fast magneto-acoustic waves by a modulated spatially non-uniform magnetic field in a plasma with a finite ratio of gas pressure to magnetic pressure is considered. The waves are excited in pairs, either pairs of the same mode, or a pair of different modes. The growth rates of the instabilities are calculated and compared with the known result for the Alfvén wave in a zero gas pressure plasma. The only waves that are found not to be excited are the slow plus fast wave pair, and the intermediate plus slow or fast wave pair (unless the waves have a component of propagation direction perpendicular to both the background magnetic field and the direction of non-uniformity of the field).

On the existence of compressional MHD oscillations in an inhomogeneous magnetoplasma

1990 ◽  
Vol 44 (2) ◽  
pp. 361-375 ◽  
Author(s):  
Andrew N. Wright
Keyword(s):  
Magnetic Field ◽  
Wave Equation ◽  
Density Distribution ◽  
Cold Plasma ◽  
Wave Equations ◽  
Perturbation Field ◽  
Plasma Density Distribution ◽  
Background Magnetic Field ◽  
Transverse Fields ◽  
The Magnetic Field

In a cold plasma the wave equation for solely compressional magnetic field perturbations appears to decouple in any surface orthogonal to the background magnetic field. However, the compressional fields in any two of these surfaces are related to each other by the condition that the perturbation field b be divergence-free. Hence the wave equations in these surfaces are not truly decoupled from one another. If the two solutions happen to be ‘matched’ (i.e. V.b = 0) then the medium may execute a solely compressional oscillation. If the two solutions are unmatched then transverse fields must evolve. We consider two classes of compressional solutions and derive a set of criteria for when the medium will be able to support pure compressional field oscillations. These criteria relate to the geometry of the magnetic field and the plasma density distribution. We present the conditions in such a manner that it is easy to see if a given magnetoplasma is able to executive either of the compressional solutions we investigate.

Schwinger effect in an instanton background with electric and magnetic fields via holography

2018 ◽  
Vol 33 (25) ◽  
pp. 1850144
Author(s):  
Maryam Gholizadeh Arashti ◽  
Majid Dehghani
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Production Rate ◽  
Pair Creation ◽  
Zero Temperature ◽  
Expectation Value ◽  
Background Magnetic Field ◽  
Electric And Magnetic Fields ◽  
Schwinger Effect ◽  
Horizon Limit

The Schwinger effect in the presence of instantons and background magnetic field was considered to study the dependence of critical electric field on instanton density and magnetic field using AdS/CFT conjecture. The gravity side is the near horizon limit of D3[Formula: see text]D(−[Formula: see text]1) background with electric and magnetic fields on the brane. Our approach is based on the potential analysis for particle–antiparticle pair at zero and finite temperatures, where the zero temperature case is a semi-confining theory. We find that presence of instantons suppresses the pair creation effect, similar to a background magnetic field. Then, the production rate will be obtained numerically using the expectation value of circular Wilson loop. The obtained production rate in a magnetic field is in agreement with previous results.

Plasma instabilities driven by pickup ions of ring-beam velocity distributions in the outer heliosheath 

2021 ◽  
Author(s):  
Ameneh Mousavi ◽  
Kaijun Liu ◽  
Sina Sadeghzadeh
Keyword(s):  
Magnetic Field ◽  
Maximum Growth ◽  
Dispersion Analysis ◽  
Maximum Growth Rate ◽  
Injection Velocity ◽  
Plasma Instabilities ◽  
Pickup Ions ◽  
Beam Velocity ◽  
Background Magnetic Field ◽  
Hybrid Simulations

&lt;p&gt;&lt;span&gt;The stability of the pickup ions in the outer heliosheath has been studied by many researchers because of its relevance to the energetic neutral atom (ENA) ribbon observed by the Interstellar Boundary EXplorer. However, previous studies are primarily limited to pickup ions of near &lt;/span&gt;&lt;span&gt;90&amp;#176; &lt;/span&gt;&lt;span&gt;pickup angles, the angle between the pickup ion injection velocity and the background, local interstellar magnetic field. Investigations on pickup ions of smaller pickup angles are still lacking. In this paper, linear kinetic dispersion analysis and hybrid simulations are carried out to examine the plasma instabilities driven by pickup ions of ring-beam velocity distributions at various pickup angles between zero and &lt;/span&gt;&lt;span&gt;90&amp;#176;&lt;/span&gt;&lt;span&gt;. &lt;/span&gt;&lt;span&gt;Parallel propagating waves are studied in the parameter regime where the parallel thermal spread of the pickup ions falls into the Alfv&amp;#233;n cyclotron stability gap. &lt;/span&gt;&lt;span&gt;The linear analysis results and hybrid simulations both show that the fastest growing modes are the right-hand helicity waves propagating in the direction of the background magnetic field, and the maximum growth rate occurs at the pickup angle of &lt;/span&gt;&lt;span&gt;82&amp;#176;&lt;/span&gt;&lt;span&gt;. The simulation results further reveal that the saturation level of the fluctuating magnetic fields for pickup angles below &lt;/span&gt;&lt;span&gt;45&amp;#176; &lt;/span&gt;&lt;span&gt;is higher than that for pickup angles above &lt;/span&gt;&lt;span&gt;45&amp;#176;&lt;/span&gt;&lt;span&gt;. So, the scattering of pickup ions at near zero pickup angles is likely more pronounced than that at near &lt;/span&gt;&lt;span&gt;90&amp;#176; &lt;/span&gt;&lt;span&gt;pickup angles&lt;/span&gt; .&lt;/p&gt;

HelioSwarm: The Nature of Turbulence in Space Plasmas

2021 ◽  
Author(s):  
Harlan Spence ◽  
Kristopher Klein ◽  
HelioSwarm Science Team
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Large Scale ◽  
Solar Wind Plasma ◽  
Turbulent Energy ◽  
Space Plasmas ◽  
Plasma Parameters ◽  
Astrophysical Plasmas ◽  
Ion Distributions ◽  
Background Magnetic Field

&lt;p&gt;Recently selected for phase A study for NASA&amp;#8217;s Heliophysics MidEx Announcement of Opportunity, the HelioSwarm Observatory proposes to transform our understanding of the physics of turbulence in space and astrophysical plasmas by deploying nine spacecraft to measure the local plasma and magnetic field conditions at many points, with separations between the spacecraft spanning MHD and ion scales.&amp;#160;&amp;#160;HelioSwarm resolves the transfer and dissipation of turbulent energy in weakly-collisional magnetized plasmas with a novel configuration of spacecraft in the solar wind. These simultaneous multi-point, multi-scale measurements of space plasmas allow us to reach closure on two science goals comprised of six science objectives: (1) reveal how turbulent energy is transferred in the most probable, undisturbed solar wind plasma and distributed as a function of scale and time; (2) reveal how this turbulent cascade of energy varies with the background magnetic field and plasma parameters in more extreme solar wind environments; (3) quantify the transfer of turbulent energy between fields, flows, and ion heat; (4) identify thermodynamic impacts of intermittent structures on ion distributions; (5) determine how solar wind turbulence affects and is affected by large-scale solar wind structures; and (6) determine how strongly driven turbulence differs from that in the undisturbed solar wind.&amp;#160;&lt;/p&gt;

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