Publications of Hans G. Embacher

2003

Articles
  • S. Kreidl, G. Grübl, H. G. Embacher, Bohmian arrival time without trajectories, Journal of Physics A. Mathematical and General 36, 8851-8865 (2003) URL Alternative URL (local copy) Preprint Identifier; doi:10.1088/0305-4470/36/33/309.

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    The computation of detection probabilities and arrival time distributions within Bohmian mechanics in general needs the explicit knowledge of a relevant sample of trajectories. Here it is shown how for one-dimensional systems and rigid inertial detectors these quantities can be computed without calculating any trajectories. An expression in terms of the wavefunction Ψ and its spatial derivative ∂x Ψ, both restricted to the boundary of the detector's spacetime volume, is derived for the general case, where the probability current at the detector's boundary may vary its sign.

1995

Dissertation
  • H. G. Embacher, Multiplikation und asymptotische Entwicklung von Distributionen in der (zwei-dimensionalen) Quantenfeldtheorie (1995) Alternative URL (local copy).

1992

Articles
  • H. G. Embacher, G. Grübl, M. Oberguggenberger, Products of Distributions in Several Variables and Applications to Zero-Mass QED_2, Journal for Analysis and its Applications 11, 437-454 (1992)  Alternative URL (local copy).

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    We study products of distributions in serveral variables, having in mind applications to quantum electrodynamics. We introduce a new product, the parameter product, and relate it to known ones. It allows us to rigorously interpret and evaluate products arising in the computations of the one-loop vacuum polarization of zero-mass QED2 , thereby avoiding the occurrence of renormalization ambiguities from the very beginning.

1991

Articles
  • H. G. Embacher, G. Grübl, Fourier representation for the two-point function of the two-dimensional massless scalar field, Letters in Mathematical Physics 22 3, 235-238 (1991)  Alternative URL (local copy); doi:10.1007/BF00403550.

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    The Fourier transform of the (indefinite metric) Wightman two-point function - (1/4π) ln( - x2 + i ε x0 ) |{ε↓0} of a free massless scalar quantum field in two-dimensional spacetime has been inconsistently reported by various authors. We compute the correct one from the definition of the Fourier transform of tempered distributions.

1990

Articles
  • M. Ritter, F. Lang, G. Grübl, H. G. Embacher, Determination of cell membrane resistance in cultured renal epithelioid (MDCK) cells. effects of cadmium and mercury ions, Pflügers Archiv European Journal of Physiology 417 1, 29-36 (1990)  Alternative URL (local copy); doi:10.1007/BF00370765.

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    Previous studies have indicated that the cell membrane of Madin Darby Canine Kidney (MDCK) cells is hyperpolarized by a number of hormones and trace elements, in parallel with an enhancement of potassium selectivity. Without knowledge of the cell membrane resistance (Rm), however, any translation of potassium selectivity into potassium conductance remains equivocal. The present study was performed to determine the Rm of MDCK cells by cellular cable analysis. To this end, three microelectrodes were impaled into three different cells of a cell cluster; current was injected via one microelectrode and the corresponding voltage deflections measured by the other two microelectrodes. In order to extract the required specific resistances, the experimental data were analysed mathematically in terms of an electrodynamical model derived from Maxwell's equations. As a result, a mean Rm of 2.0±0.2 kΩcm² and an intercellular coupling resistance (Rc) of 6.1±0.8 MΩ were obtained at a mean potential difference across the cell membrane of -47.0±0.6 mV. An increase of the extracellular K+ concentration from 5.4 to 20 mmol/l depolarized the cell membrane by 16.2±0.5 mV and decreased Rm by 30.6±3.0%; 1 mmol/l barium depolarized the cell membrane by 20.1±1.1 mV and increased Rm by 75.9±14.3%. Omission of extracellular bicarbonate and carbon dioxide at constant extracellular pH caused a transient hyperpolarization (up to –60.4±1.4 mV), a decrease of Rm (by 75±4.5%) and a decrease of Rc (by 23.1±8.4%). The changes in Rm and Rc were probably the result of intracellular alkalosis. Cadmium ions (1 μmol/l) led to a sustained, reversible hyperpolarization (to –64.8±1.3 mV) and to a decrease of Rm (by 77.0±2.7%); mercury ions (1 μmol/l) cause a sustained hyperpolarization (to –60.1±1.2 mV) and a decrease of Rm (by 76.3±3.9%). Neither manoeuvre significantly altered Rc. We have previously shown that both cadmium and mercury hyperpolarize the cell membrane potential and increase its potassium selectivity; the decrease of the Rm observed in the present study indicates that these effects are due to an increase of the potassium-selective conductance of the cell membrane.

1988

Articles
  • H. G. Embacher, G. Grübl, Axial anomaly and Schwinger terms in two-dimensional general quantum field theory, Physical Review D (Particles and Fields) 38 2, 597-597 (1988) URL Alternative URL (local copy); doi:10.1103/PhysRevD.38.597.

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    We compute the vacuum expectation value (Ω, jμ(x) jν(y) Ω) ≡ Jμν(x-y) for a relativistic, Hermitian, not necessarily local vector field in two-dimensional space-time when ∂μ Jμν = ∂μ Jνμ = ∂μ εαμ Jαν = ∂μ εαμ Jνα = 0 holds in S’(R²), the space of tempered distributions. As the space-time symmetry group of the model we take the inhomogeneous proper orthochronous Lorentz group P+. (Ω, Tjμ (x) jν (y) Ω) is verified to have anomalous (axial-)vector Ward identities due to nonvanishing equal-time current-current commutators. Additional conditions on jμ are specified which imply that jμ is a free zero-mass Wightman field with ∂μ jμ = ∂μ ενμ jν = 0.
  • H. G. Embacher, G. Grübl, R. Patek, Explicit Soliton Solution to the Bosonized Jackiw-Rebbi Model with Fermion Number 1/2, Europhysics Letters 5, 497-501 (1988) Alternative URL (local copy).

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    We study the half-integer charged-soliton sector of the (φ)4 Higgs-type scalar field model with Yukawa coupling to a massless Dirac field in 2-dimensional space-time in its bozonized version: we find the one-soliton solution to the coupled nonlinear field equations of the model which represents the quantum soliton with fermion number 1/2 and compute its mass. A comparison with the corresponding c-number solution of the fermionic model is included.

1986

Articles
  • H. G. Embacher, G. Grübl, R. Patek, Gauge-invariant energy-momentum tensor for massive QED, Physical Review D (Particles and Fields) 33, 1162-1165 (1986) URL Alternative URL (local copy); doi:10.1103/PhysRevD.33.1162.

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    For massive QED with a gauge-fixing term a candidate for the energy-momentum tensor is presented. Both cases of scalar and spinor matter fields are treated. The energy-momentum tensor is invariant under the restricted gauge transformations which exist in that model. This property guarantees that the unphysical scalar photons do not contribute to the energy-momentum densities. The difference between the translational generators and the energy-momentum observables is pointed out.

1984

Diploma Thesis
  • H. G. Embacher, Die Beschreibung hadronischer Prozesse bei tiefinelastischer Lepton-Streuung und Elektron-Positron-Vernichtung durch das Parton-Modell (1984)