摘要:

In collisions of very heavy ions “supercritically” strong electric fields can be created transiently. In the presence of a supercritical field the neutral vacuum state of QED becomes unstable and decays into a charged vacuum, signalled by the spontaneous emission of positrons. Consequently the emission of positrons is strongly enhanced in high-Zcollisions. Clear experimental signals for spontaneous positron creation are still missing and could only be expected from collisions with a prolonged time scale. We discuss possible scenarios for this to happen and indirect methods to perform a spectroscopy of superheavy quasimolecules. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1374961

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

A measurement of the2SLamb shift (2S−2Penergy difference) in muonic hydrogen(&mgr;−p)is being prepared at the Paul Scherrer Institute (PSI). The goal of the experiment is to measure the Lamb shift with 30 ppm precision and to deduce the root mean square (rms) proton charge radius with10−3relative accuracy, 20 times more precise than presently known. The experiment is based on the availability of long-lived metastable muonic hydrogen atoms in the2Sstate which has been investigated in a recent series of experiments at PSI. From the low-energy part of the initial kinetic energy distribution of&mgr;p(2S)atoms we determined the fraction of long-lived&mgr;p(2S)to be ∼1.5&percent; forH2gas pressures between 1 and 64 hPa. Another analysis involving&mgr;p(1S)with a kinetic energy of 0.9 keV originating from quenching of thermalized&mgr;p(2S)via the resonant process&mgr;p(2S)+H2→{[(pp&mgr;)+]*pee}*→&mgr;p(1S)+p+&ellip;+2&hthinsp;keVgives the same result. This is the first direct observation of long-lived&mgr;p(2S)atoms. The realization of the &mgr;p Lamb shift experiment involves a new low-energy negative muon beam with entrance detectors for keV-muons, a xenon gas-proportional-scintillation-chamber (GPSC) read out by a microstrip-gas-chamber (MSGC) for the detection of 2 keV X-rays, and a randomly triggered 3-stage laser system providing 0.5 mJ, 7 ns laser pulses at 6.02 &mgr;m wavelength. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1374962

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The Casimir force results from the alteration by boundaries of the zero point electromagnetic energy. We have used the atomic force microscope to make precision measurements of the Casimir force between a large gold coated sphere and a flat plate. The complete dielectric spectrum of the metal is used in the comparison of theory to the experiment. The average statistical precision is around 1&percent; of the forces measured at the closest separation. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1374963

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

A survey is given of applications of the “string-inspired” worldline formalism to the computation of amplitudes and effective actions in QED. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1374964

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The dynamics of polarized photons can be effectively modeled by means of a generalized time-evolution, that describes phenomena leading to loss of phase coherence and dissipation. High sensitive experiments, both in the laboratory and in space, will soon be able to put stringent bounds on these non-standard effects. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1374965

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The self-energy correction to the Coulomb part of the electron-electron interaction (self-energy screening) is evaluated. We consider only the monopole term, which is the only one present in many cases, and the direct term. We evaluate the energy shift due to a1s1/2,2s1/2,2p1/2,or2p3/2electron screening a1s1/2,2s1/2,2p1/2,or2p3/2electron, for nuclear chargeZin the range5⩽Z⩽92.A detailed comparison with other calculations is made. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1374966

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

We demonstrate that at pressures not exceeding a few bars and temperatures below 15&hthinsp;°K the semiclassical theory of antiprotonic helium spectral line shape agrees with the quasistatic model, and discuss the application of the latter to the shift and broadening of hyperfine transition lines. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1374967

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

Quantum algebraic observables representing localization in space-time of a Dirac electron are defined. Inertial motion of the electron is represented in the quantum algebra with electron mass acting as the generator of motion. Since transformations to uniformly accelerated frames are naturally included in this conformally invariant description, the quantum algebra is also able to deal with uniformly accelerated motion. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1374968

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The construction of low-energy effective actions in QED for several types of external conditions is reviewed. Emphasis is put on the application of these effective actions to a variety of physical effects which represent a manifestation of vacuum polarization. Soft-photon interactions with external electromagnetic fields and/or a heat bath are described, pair production at finite temperature is discussed, and finally a glance at photon-neutrino interactions is provided. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1374969

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

After a brief description of the now operating PVLAS apparatus and of its goals, we present and discuss the preliminary experimental results obtained from the first recent measurement runs conducted with the complete setup. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1374970

出版商:AIP    

年代:1901

数据来源: AIP