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Generalized Unruh effect and Lamb shift for atoms on arbitrary stationary trajectories  [PDF]
Juergen Audretsch,Rainer Mueller,Markus Holzmann
Physics , 1995, DOI: 10.1088/0264-9381/12/12/010
Abstract: We study the spontaneous de-excitation and excitation of accelerated atoms on arbitrary stationary trajectories (``generalized Unruh effect''). We consider the effects of vacuum fluctuations and radiation reaction separately. We show that radiation reaction is generally not altered by stationary acceleration, whereas the contribution of vacuum fluctuations differs for all stationary accelerated trajectories from its inertial value. Spontaneous excitation from the ground state occurs for all { accelerated stationary} trajectories and is therefore the ``normal case''. We furthermore show that the radiative energy shift (``Lamb shift'') of a two-level atom is modified by acceleration for all stationary trajectories. Again only vacuum fluctuations give rise to the shift. Our results are illustrated for the special case of an atom in circular motion, which may be experimentally relevant.
Lamb Shift of Energy Levels in Quantum Rings  [PDF]
G. Yu. Kryuchkyan,O. Kyriienko,I. A. Shelykh
Physics , 2014, DOI: 10.1088/0953-4075/48/2/025401
Abstract: We study the vacuum radiative corrections to energy levels of a confined electron in quantum rings. The calculations are provided for the Lamb shift of energy levels in low-momentum region of virtual photons and for both one-dimensional and two-dimensional quantum rings. We show that contrary to the well known case of a hydrogen atom the value of the Lamb shift increases with the magnetic momentum quantum number m. We also investigate the dependence of the Lamb shift on magnetic flux piercing the ring and demonstrate a presence of magnetic-flux-dependent oscillations. For one-dimensional ring the value of the shift strongly depends on the radius of the ring. It is extremely small for semiconductor rings but can attain measurable quantities in natural organic ring-shape molecules, such as benzene, cycloalcanes and porphyrins.
The Lamb Shift of Excited S-Levels in Hydrogen and Deuterium Atoms  [PDF]
Savely G. Karshenboim
Physics , 1996, DOI: 10.1007/s004600050116
Abstract: A specific combination of $s$-state Lamb shift $\Delta E_L(1s_{1/2}) - n^3 \Delta E_L(ns_{1/2})$ is considered. Its value is calculated both in the hydrogen and deuterium atoms for $n$ up to 12. The result inludes all correction which can contribute $1 kHz$ and particulary: one-loop self energy and vacuum polarization, two-loop contribution. Nuclear finite-size corrections for the isotopic difference of the combination are also evaluated.
Orbital Lamb shift and mixing of the pseudo-zero-mode Landau levels in ABC-stacked trilayer graphene  [PDF]
K. Shizuya
Physics , 2012, DOI: 10.1103/PhysRevB.87.085413
Abstract: In a magnetic field graphene trilayers support a characteristic multiplet of 12 zero(-energy)-mode Landau levels with a threefold degeneracy in Landau orbitals. It was earlier noted for bilayer graphene that Coulombic vacuum fluctuations, specific to graphene, lift the orbital degeneracy of such zero-energy modes and that these Lamb-shfted" orbital modes, with filling, get mixed via the Coulomb interaction. It is pointed out that analogous orbital Lamb shift and mixing of zero-mode levels can also take place, with an enriched symmetry content, in ABC-stacked trilayer graphene; and its consequences are discussed in the light of experimental results.
The Lamb shift in de Sitter spacetime  [PDF]
Wenting Zhou,Hongwei Yu
Physics , 2010, DOI: 10.1103/PhysRevD.82.124067
Abstract: We study the Lamb shift of both freely-falling and static two-level atoms in interaction with quantized conformally coupled massless scalar fields in the de Sitter-invariant vacuum. We find that the Lamb shifts of both freely-falling and static atoms are in structural similarity to that of an inertial atom immersed in a thermal bath in a Minkowski spacetime. For the freely-falling atom, the Lamb shift gets a correction as if it was immersed in a thermal bath at the Gibbons-Hawking temperature, thus revealing clearly the intrinsic thermal nature of de Sitter spacetime. For the static atom, the Lamb shift is affected by a combination of the effect of the intrinsic thermal nature of de Sitter spacetime and the Unruh effect associated with the inherent acceleration of the atom.
Lamb Shift for static atoms outside a Schwarzschild black hole  [PDF]
Wenting Zhou,Hongwei Yu
Physics , 2010, DOI: 10.1103/PhysRevD.82.104030
Abstract: We study, by separately calculating the contributions of vacuum fluctuations and radiation reaction to the atomic energy level shift, the Lamb shift of a static two-level atom interacting with real massless scalar fields in the Boulware, Unruh and Hartle-Hawking vacuums outside a Schwarzschild black hole. We find that in the Boulware vacuum, the Lamb shift gets a correction arising as a result of the backscattering of vacuum field modes off the space-time curvature, which is reminiscent of the correction to the Lamb shift induced by the presence of cavities. However, when the Unruh and Hartle-Hawking vacua are concerned, our results show that the Lamb shift behaves as if the atom were irradiated by a thermal radiation or immersed in a thermal bath at the Hawking temperature, depending on whether the scalar field is in the Unruh or the Hartle-Hawking vacuum. Remarkably, the thermal radiation is always backscattered by the space-time geometry.
Structure and the Lamb-shift-like quantum splitting of the pseudo-zero-mode Landau levels in bilayer graphene  [PDF]
K. Shizuya
Physics , 2012, DOI: 10.1103/PhysRevB.86.045431
Abstract: In a magnetic field bilayer graphene supports an octet of zero-energy Landau levels with an extra twofold degeneracy in Landau orbitals n=0 and n=1. It is shown that this orbital degeneracy is lifted due to Coulombic quantum fluctuations of the valence band (the Dirac sea); this is a quantum effect analogous to the Lamb shift in the hydrogen atom. A detailed study is made of how these zero-energy levels evolve, with filling, into a variety of pseudo-zero-mode Landau levels in the presence of possible spin and valley breaking and Coulomb interactions, and a comparison is made with experimental results.
The Lamb Shift in Dimensional Regularization  [PDF]
A. Pineda,J. Soto
Physics , 1997, DOI: 10.1016/S0370-2693(97)01537-2
Abstract: We present a simple derivation of the Lamb shift using effective field theory techniques and dimensional regularisation.
Hydrogen Atom Spectrum and the Lamb Shift in Noncommutative QED  [PDF]
M. Chaichian,M. M. Sheikh-Jabbari,A. Tureanu
Physics , 2000, DOI: 10.1103/PhysRevLett.86.2716
Abstract: We have calculated the energy levels of the hydrogen atom and as well the Lamb shift within the noncommutative quantum electrodynamics theory. The results show deviations from the usual QED both on the classical and on the quantum levels. On both levels, the deviations depend on the parameter of space/space noncommutativity.
Lamb Shift in Muonic Hydrogen  [PDF]
E. Borie
Physics , 2004, DOI: 10.1103/PhysRevA.71.032508
Abstract: The Lamb shift in muonic hydrogen continues to be a subject of experimental and theoretical investigation. Here my older work on the subject is updated to provide a complementary calculation of the energies of the 2p-2s transitions in muonic hydrogen.
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