Browsing by Author "Weigel, H."

Now showing 1 - 8 of 8
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    Attractive electromagnetic Casimir stress on a spherical dielectric shell
    (Elsevier, 2013) Graham, N.; Quandt, M.; Weigel, H.
    Based on calculations involving an idealized boundary condition, it has long been assumed that the stress on a spherical conducting shell is repulsive. We use the more realistic case of a Drude dielectric to show that the stress is attractive, matching the generic behavior of Casimir forces in electromagnetism. We trace the discrepancy between these two cases to interactions between the electromagnetic quantum fluctuations and the dielectric material.
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    Emerging translational variance : vacuum polarization energy of the 𝜙6 kink
    (Hindawi, 2017-07-30) Weigel, H.
    We propose an efficient method to compute the vacuum polarization energy of static field configurations that do not allow decomposition into symmetric and antisymmetric channels in one space dimension. In particular, we compute the vacuum polarization energy of the kink soliton in the 𝜙6 model. We link the dependence of this energy on the position of the center of the soliton to the different masses of the quantum fluctuations at negative and positive spatial infinity.
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    Heavy baryons with strangeness in a soliton model
    (Elsevier, 2015-09) Blanckenberg, J. P.; Weigel, H.
    We present results from a chiral soliton model calculation for the spectrum of baryons with a single heavy quark (charm or bottom) and non-zero strangeness. We treat the strange components within a three flavor collective coordinate quantization of the soliton that fully accounts for light flavor symmetry breaking. Heavy baryons emerge by binding a heavy meson to the soliton. The dynamics of this heavy meson is described by the heavy quark effective theory with finite mass effects included.
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    Quantum stabilization of a hedgehog type of cosmic string
    (Elsevier, 2017) Quandt, M.; Graham, N.; Weigel, H.
    Within a slightly simplified version of the electroweak standard model we investigate the stabilization of cosmic strings by fermion quantum fluctuations. Previous studies of quantum energies considered variants of the Nielsen–Olesen profile embedded in the electroweak gauge group and showed that configurations are favored for which the Higgs vacuum expectation value drops near the string core and the gauge field is suppressed. This work found that the strongest binding was obtained from strings that differ significantly from Nielsen–Olesen configurations, deforming essentially only the Higgs field in order to generate a strong attraction without inducing large gradients. Extending this analysis, we consider the leading quantum cor-rection to the energy per unit length of a hedgehog type string, which, in contrast to the Nielsen–Olesen configuration, contains a pseudoscalar field. To employ the spectral method we develop the scattering and bound state problems for fermions in the background of a hedgehog string. Explicit occupation of bound state levels leads to strings that carry the quantum numbers of the bound fermions. We discuss the pa-rameter space for which stable, hedgehog type cosmic strings emerge and reflect on phenomenological consequences of these findings.
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    Spectral methods for coupled channels with a mass gap
    (American Physical Society, 2018) Weigel, H.; Quandt, M.; Graham, N.
    We develop a method to compute the vacuum polarization energy for coupled scalar fields with different masses scattering off a background potential in one space dimension. As an example we consider the vacuum polarization energy of a kinklike soliton built from two real scalar fields with different mass parameters.
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    Vacuum polarization energy for general backgrounds in one space dimension
    (Elsevier, 2017) Weigel, H.
    For field theories in one time and one space dimensions we propose an efficient method to compute the vacuum polarization energy of static field configurations that do not allow a decomposition into symmetric and anti-symmetric channels. The method also applies to scenarios in which the masses of the quantum fluctuations at positive and negative spatial infinity are different. As an example we compute the vacuum polarization energy of the kink soliton in the ø⁶ model. We link the dependence of this energy on the position of the soliton to the different masses.
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    Vacuum polarization energy of the Shifman–Voloshin soliton
    (Elsevier, 2018) Weigel, H.; Graham, N.
    We compute the vacuum polarization energy of soliton configurations in a model with two scalar fields in one space dimension using spectral methods. The second field represents an extension of the conventional ϕ4 kink soliton model. We find that the vacuum polarization energy destabilizes the soliton except when the fields have identical masses. In that case the model is equivalent to two independent ϕ4 models.
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    Wave-packet scattering off the kink-solution
    (2011) Abdelhady, A. M. H. H.; Weigel, H.
    We investigate the propagation of a wave-packet in the φ4 model. We solve the time-dependent equation of motion for two distinct initial conditions: The wave-packet in a trivial vacuum background and in the background of the kink soliton solution. We extract the scattering matrix from the wave-packet in the kink background at very late times and compare it with the result from static potential scattering in the small amplitude approximation. We vary the size of the initial wave-packet to identify nonlinear effects as, for example, the replacement of the center of the kink. © 2011 World Scientific Publishing Company.