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1 
Effects of vacuum polarization in strong external fieldsLu, T.M. January 1976 (has links)
ThesisWisconsin. / Vita. Includes bibliographical references (leaf 57).

2 
The casimir effect /Lang, Andrew January 1998 (has links)
Thesis (Ph. D.)University of MissouriColumbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 8485). Also available on the Internet.

3 
The casimir effectLang, Andrew January 1998 (has links)
Thesis (Ph. D.)University of MissouriColumbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 8485). Also available on the Internet.

4 
Gauge invariant calculation of vacuum polarization phenomena in quantum electrodynamicsHerrera, John Chardon January 1964 (has links)
Thesis (Ph.D.)Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at openhelp@bu.edu. Thank you. / A technique capable of describing in detail the various phenomena arising in the limit of low energy photons because of the polarization of the vacuum is obtained by quantizing the gauge invariant effective interaction Lagrangian. This approach then permits the use of the standard covariant calculational tools of Quantum Electrodynamics.
We first apply this technique to the computation of the differential cross section for low energy photonphoton scattering. The well known Euler cross section is thereby derived in a direct manner.
As a second example, the probability of the triple breakup of a free photon because of vacuum polarization is explicitly shown to vanish. This, however, is primarily due to the kinematics of the photon breakup.
For a third application we calculate the differential cross section for the scattering of a low energy photon from the Coulomb field of a nucleus, that is, Delbruck scattering. Here the exact low energy differential cross section is obtained. However, though the present technique determines completely the angular dependence, it is necessary to introduce a momentum cutoff in the Coulomb field in order to obtain a finite value for the coefficient in front of the angular dependence. A comparison of the resulting expression for the cross section with that for forward scattering given by Rohrlich and Gluckstern (1952) gives the numerical value of this coefficient.
A brief comparison between the angular distribution for Delbruck scattering and that for a combination of an electric and magnetic dipole radiator is presented. / 20310101

5 
Vacuum polarization and Hawking radiationRahmati, Shohreh January 2012 (has links)
Quantum gravity is one of the interesting fields in contemporary physics which is
still in progress. The purpose of quantum gravity is to present a quantum description
for spacetime at 10 33cm or find the `quanta' of gravitational interaction.. At
present, the most viable theory to describe gravitational interaction is general relativity
which is a classical theory. Semiclassical quantum gravity or quantum field
theory in curved spacetime is an approximation to a full quantum theory of gravity.
This approximation considers gravity as a classical field and matter fields are
quantized. One interesting phenomena in semiclassical quantum gravity is Hawking
radiation. Hawking radiation was derived by Stephen Hawking as a thermal emission
of particles from the black hole horizon. In this thesis we obtain the spectrum of
Hawking radiation using a new method.
Vacuum is defined as the possible lowest energy state which is filled with pairs of
virtual particleantiparticle. Vacuum polarization is a consequence of pair creation
in the presence of an external field such as an electromagnetic or gravitational field.
Vacuum polarization in the vicinity of a black hole horizon can be interpreted as
the cause of the emission from black holes known as Hawking radiation. In this
thesis we try to obtain the Hawking spectrum using this approach. We reexamine
vacuum polarization of a scalar field in a quasilocal volume that includes the horizon.
We study the interaction of a scalar field with the background gravitational field of
the black hole in the desired quasilocal region. The quasilocal volume is a hollow
cylinder enclosed by two membranes, one inside the horizon and one outside the
horizon. The net rate of particle emission can be obtained as the difference of the
vacuum polarization from the outer boundary and inner boundary of the cylinder.
Thus we found a new method to derive Hawking emission which is unitary and well
defined in quantum field theory. / ix, 109 leaves : ill. ; 29 cm

6 
WeakEquivalence Principle Violation and Mass Change of Charged Matter Due to Vacuum PolarizationTajmar, Martin 08 March 2016 (has links) (PDF)
Vacuum polarization by electric fields is a well established fact. Assuming that antimatter has negative gravitational properties, the fluctating electric dipoles from the quantum vacuum may also have gravitational dipolar properties. A model is developed that describes how electric fields could gravitationally polarize the vacuum causing gravitational screening or antiscreening effects. This leads to a violation of the Weak Equivalence Principle or a general mass change most notabily for elementary particles, such as the electron or positron, below but close to measured boundaries. Also a gravitational vacuum torque is predicted to act on a charged capacitor perpendicular to a gravitational field. The predictions could be verified by future laboratory experiments that could contribute on our understanding of the gravitational properties of antimatter.

7 
A convergent reformulation of perturbative QCDAlves, Ricardo Joao Gaio January 2000 (has links)
We present and explore a new formulation of perturbative QCD based not on the renormalised coupling but on the dimensional transmutation parameter of the theory and the property of asymptotic scaling. The approach yields a continued function, the iterated function being that involved in the solution of the twoloop βfunction equation. In the socalled largeb limit the continued function reduces to a continued fraction and the successive approximants are diagonal Padé approximants. We investigate numerically the convergence of successive approximants using the leadingb approximation, motivated by renormalons, to model the allorders result. We consider the Adler Dfunction of vacuum polarisation, the Polarised Bjorken and GrossLlewellyn Smith sum rules, the (unpolarised) Bjorken sum rule, and the Minkowskian quantities R(_r) and the Rratio of e(^+)e(^) annihilation. In contrast to diagonal Fade approximants the truncated continued function method gives remarkably stable largeorder approximants in cases where infrared renormalon effects are important. We also use the new approach to determine the QCD fundamental parameters from the R(_r) and the Rratio measurements, where we find Ā(^(3))(_MS)=516±48 MeV (which yields a(_s)(µ=m(_r))=0.360(^+0.021)(_=0.020)), and Ā(^(5))(_MS)=299(^+6)(_7) MeV (which yields a(_s)(µ=m(_zo)=0.1218±0.0004), respectively. The evolution of the former value to the m(_zo) energy results in a(_s)(µ= m(_zo)) = 0.123 ± 0.002. These values are in line with other determinations available in the literature. We implement the Complete Renormalisation Group Improvement (CORGI) scheme throughout all the calculations. We report on how the mathematical concept of Stieltjes series can be used to assess the convergence of Padé approximants of perturbative series. We find that the combinations of UV renormalons which occur in perturbative QCD may or may not be Stieltjes series depending on the renormalisation scheme used.

8 
Polarizace vakua v Coulombickém poli / Polarizace vakua v Coulombickém poliŠimsa, Daniel January 2013 (has links)
In the present work the vacuum polarization and the circular dichroism of hydrogenlike atoms are studied. We derive equations for the Fourier transforma tion of the vacuum expectation value of the charge density. We use it to derive Uehling potential and calculate energy shifts caused by it. Then we discuss effects of vacuum polarization in higher orders of α. In second part we define circular dichroism and we express it in terms of reduced matrix elements. Then we derive the formula for parity vilating potential which is generated by weak interaction and together with other results we use it to find the expression for circular dichro ism in terms of hydrogen radial functions. 1

9 
Jemné efekty v atomech a molekulách / Subtle Effects in Atmos and MoleculesŠimsa, Daniel January 2018 (has links)
The thesis is divided into two parts. The first part deals with radiative cor rections in muonic hydrogen. The effect of vacuum polarization is studied, and the simplified derivation of the WichmannKroll potential is presented. The en ergy shift caused by vacuum polarization to the Lamb shift in muonic hydrogen is calculated and it agrees with results in literature. Further, the concept of the extended Bethe logarithm is introduced and its advantages are shown and used to calculate the combined selfenergy vacuum polarization contribution to the Lamb shift in muonic hydrogen. The results given here are more accurate and somewhat different from others given in literature. In the second part, the groundstate en ergy splitting due to the tunneling in a twodimensional doublewell potential is calculated. A systematic WKB expansion of the energy splitting is given. An in terplay between curvature of the classical tunneling path and quantum nature of motion is observed. A series is found that describes systems with strong coupling like the proton transfer in malonaldehyde. The results show a strong sensitivity of the splitting on slight variations of the parameters entering the Hamiltonian linearly. This indicates a presence of quantum chaos in this problem. 1

10 
Applications of analyticity to scalar meson phenomenologyCherry, Stuart Nicholas January 2001 (has links)
The scalar mesons have caused much debate amongst hadronic physicists for many years. Even today the number of scalars is hotly contested, and there is almost no agreement on the composition of any of the experimentally observed states, except perhaps for the K*(_0) (1430). This thesis attempts to shed light on both of these problems via the application of analyticity to two different quantities. Recently a number of authors have proposed the existence of a light, strange, scalar meson known as the k. We perform a direct search of the best available πK scattering data to determine whether or not this resonance exists. This is done by constructing contour integrals from these data and determining the number of poles present inside the contour. We do not need to model either the internal dynamics of the state nor the form of the background scattering. The number of poles found tells us the number of resonances present and their positions allow us to estimate the resonance parameters. We find that there is only one resonance in scalar πK scattering below 1800 MeV and this is identified with the established K*(_0)(1430). We find no evidence for the k. Secondly, applying Cauchy's Theorem to the vacuum polarisation function leads to a relation between experimental and theoretical integrals known as a Finite Energy Sum Rule (FESR). FESRs are used to explore the scalar, isoscalar nonstrange current and allow us to determine which of the experimentally observed scalar, isoscalar mesons is most likely to be the uũ + dd state. We find that the lightest scalar, isoscalar uũ dd state is not the fo(980) as suggested by some authors, but is rather the light, broad object known as the fo(400  1200). We are also able to estimate the average light quark mass and find m(_q)(l GeV(^2)) = 4.7 ± 0.9 MeV which is consistent with the recent estimates of this quantity from unquenched lattice QCD.

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