4,265 research outputs found
Detection of QED vacuum nonlinearities in Maxwell's equations by the use of waveguides
We present a novel method for detecting nonlinearities, due to quantum
electrodynamics through photon-photon scattering, in Maxwell's equation. The
photon-photon scattering gives rise to self-interaction terms, which are
similar to the nonlinearities due to the polarisation in nonlinear optics.
These self-interaction terms vanish in the limit of parallel propagating waves,
but if instead of parallel propagating waves the modes generated in wavesguides
are used, there will be a non-zero total effect. Based on this idea, we
calculate the nonlinear excitation of new modes and estimate the strength of
this effect. Furthermore, we suggest a principal experimental setup.Comment: 4 pages, REVTeX3. To appear in Phys. Rev. Let
A possibility to measure elastic photon--photon scattering in vacuum
Photon--photon scattering in vacuum due to the interaction with virtual
electron-positron pairs is a consequence of quantum electrodynamics. A way for
detecting this phenomenon has been devised based on interacting modes generated
in microwave waveguides or cavities [G. Brodin, M. Marklund and L. Stenflo,
Phys. Rev. Lett. \textbf{87} 171801 (2001)]. Here we materialize these ideas,
suggest a concrete cavity geometry, make quantitative estimates and propose
experimental details. It is found that detection of photon-photon scattering
can be within the reach of present day technology.Comment: 7 pages, 3 figure
Extending the Higgs sector: an extra singlet
An extension of the Standard Model with an additional Higgs singlet is
analyzed. Bounds on singlet admixture in 125 GeV h boson from electroweak
radiative corrections and data on h production and decays are obtained.
Possibility of double h production enhancement at 14 TeV LHC due to heavy higgs
contribution is considered.Comment: 18 pages, 7 figures. v2: one equation added; references received
after the publication of v1 are adde
Theory of Z boson decays
The precision data on Z boson decays from LEP-I and SLC colliders are
compared with the predictions based on the Minimal Standard Theory. The Born
approximation of the theory is based on three most accurately known
observables: G_mu -- the four fermion coupling constant of muon decay, m_Z --
the mass of the Z boson, and alpha(m_Z) -- the value of the running fine
structure constant at the scale of m_Z. The electroweak loop corrections are
expressed, in addition, in terms of the masses of higgs, m_H, of the top and
bottom quarks, m_t and m_b, and of the strong interaction constant
alpha_s(m_Z). The main emphasis of the review is focused on the
one-electroweak-loop approximation. Two electroweak loops have been calculated
in the literature only partly. Possible manifestations of new physics are
briefly discussed.Comment: 80 pages, 16 figures, accepted in Reports on Progress in Physic
New Physics at 1 TeV?
If decays of a heavy particle S are responsible for the diphoton excess with
invariant mass 750 GeV observed at the 13 TeV LHC run, it can be easily
accomodated in the Standard Model. Two scenarios are considered: production in
gluon fusion through a loop of heavy isosinglet quark(s) and production in
photon fusion through a loop of heavy isosinglet leptons. In the second case
many heavy leptons are needed or/and they should have large electric charges in
order to reproduce experimental data on .Comment: 7 pages, 4 figures, 1 tabl
Electroweak radiative corrections in Z boson decays
Contribution to A.D.Sakharov memorial volume. A detailed review of the
electroweak radiative corrections to the Z-boson decays in the framework of the
Minimal Standard Modelm (MSM) is presented. After a short historical
introduction we describe the optimal parametrization of the MSM, especially of
the Born approximation, and derive expressions for the one-loop electroweak
corrections. Finally a global fit of all relevant experimental data is
performed, resulting in fitted values of the top-quark mass, m_t, and strong
coupling constant /alpha_s. Allowed range for the value of the Higgs mass, m_H,
is discussed. Various details of calculations are described in 16 appendices.Comment: 98 pages,21 EPS and PS figures,uses epsf.sty, separate file with the
tared, compressed and uuencoded figures is awailable at
http://wwwtheor.itep.ru/~vysotsky/figures.u
Charmed penguin versus BAU
Since the Standard Model most probably cannot explain the large value of CP
asymmetries recently observed in D-meson decays we propose the fourth
quark-lepton generation explanation of it. As a byproduct weakly mixed leptons
of the fourth generation make it possible to save the baryon number of the
Universe from erasure by sphalerons. An impact of the 4th generation on BBN is
briefly discussed.Comment: 13 pages, 3 figures, version to be published in JETP Letter
Limitations On High-frequency Permeability Of Magnetic Materials
Engineering of magnetic composites with high microwave permeability is important for EMC/EMI and other applications. One of the challenging problems is to determine constraints on the achievable high-frequency permeability of magnetic composites. The objective of the present paper is to analyze the data available from the literature on the microwave permeability constraints and derive a generalized constraint condition. It is well known that in many practical occasions the actual magnetic frequency dispersion curves differ from the Lorentzian behavior. For these cases, an integral form of the constraint may be useful. Possible applications of the integral constraint are discussed for the cases of large damping, pronounced effect of eddy currents, and inhomogeneous materials. It is shown that the derived constraint can be successfully used in these cases for both estimating microwave performance of devices containing magnetic materials and obtaining additional data on the magnetic structure of materials. © 2013 IEEE
Application Of Generalized Snoek\u27s Law Over A Finite Frequency Range: A Case Study
Generalized Snoek\u27s law proposed in an integral form by Acher and coauthors is a useful tool for investigation of high-frequency properties of magnetic materials. This integral law referred to as Acher\u27s law allows for evaluating the ultimate performance of RF and microwave devices which employ magnetic materials. It may also be helpful in obtaining useful information on the structure and morphology of the materials. The key factor in practical application of Acher\u27s law is an opportunity to employ either measured or calculated data available over a finite frequency range. The paper uses simple calculations to check the applicability of Acher\u27s law in cases when the frequency range is limited, and the magnetic loss peak is comparatively wide and has a distorted shape. The cases of large magnetic damping pronounced skin effect, and inhomogeneity of the material are considered. It is shown that in most cases calculation of the integral through fitting of actual magnetic frequency dispersion by the Lorentzian dispersion law results in accurate estimations of the ultimate high-frequency performance of magnetic materials
- …