The compatibility of free fractional charge and Dirac magnetic monopoles

The existence of a free fractionally charged particle together with a monopole that has magnetic charge $\text{g=}\text{1}\text{2e}$ poses an apparent conflict. This conflict may be resolved by enlarging the exact gauge symmetry. The resulting constraint on GUTs is discussed and illustrated with an SU(9) GUT. Under certain assumptions, SU(9) is the smallest group to satisfy the constraints.     

Dirac and Yang monopoles revisited

The Dirac monopoles in 3-space and their generalization by C.N. Yang to 5-space are observed to be just the Levi-Civita spin connections of the cylindrical Riemannian metric on the 3-and 5-dimensional punctured spaces respectively. Their straightforward generalization to higher dimensions is also investigated.      

The finite-size effects of goldstone bosons in Monte Carlo simulations

It is shown how one can, in practice, extract the value of the pion decay constant ⨍, from the finite-size behavior of the magnetic susceptibility. The method is based on a finite-size soft-pion theorem and is successfully tested on the Gell-Mann-Levy linear sigma model.     

How effective massless fermions modify the anomalous decays of the goldstone bosons

We consider the consequences of the anomalous Ward identities when both Goldstone bosons and massless fermions appear as low-energy degress of freedom in confining theories. A general procedure for evaluating the anomalous vertices of the Goldstone bosons is given. We show that these vertices can be described in a compact way. The emerging structures have an intrinsic geometrical meaning. Some particular features occuring when the massless fermions are superpartners of the Goldstone bosons are illustrated on the example of supersymmetric QCD.     

Inconsistency of QED in the presence of Dirac monopoles

A precise formulation ofU (1) local gauge invariance in QED is presented, which clearly shows that the gauge coupling associated with the unphysical longitudinal photon field is non-observable and actually has an arbitrary value. We then re-examine the Dirac quantization condition and find that its derivation involves solely the unphysical longitudinal coupling. Hence an inconsistency inevitably arises in the presence of Dirac monopoles and this can be considered as a theoretical evidence against their existence. An alternative, independent proof of this conclusion is also presented.     

Direct search for charged higgs bosons in decays of top quarks

We present a search for charged Higgs bosons in decays of pair-produced top quarks in pp collisions at sqrt[s] = 1.8 TeV recorded by the D0 detector at the Fermilab Tevatron collider. With no evidence for signal, we exclude most regions of the ( M(H+/-),tan(beta)) parameter space where the decay t--> H(+)b has a branching fraction >0.36 and B(H+/--->tau(nu)(tau)) is large.     

Observability of intermediate scale pseudo goldstone bosons through conversion into photons

Light scalar states are generically present in a large class of stringy models. It is shown that they explain the polarized photon fluxes emitted from regions of the Universe filled with a strong magnetic field. We propose a specific scenario for sufficient emission in a realistic model.     

Magnetic monopoles: Evidence since the Dirac conjecture

In the fifty-one years since its publication Dirac's magnetic monopole conjecture has stimulated a theoretical outpouring rich in variety. We review here the experimental techniques with which monopoles have been sought and we will describe the limits on monopole properties these searches have established.     

Search for intermediate mass magnetic monopoles and nuclearites with the SLIM experiment

SLIM is a large area experiment (440 m²) installed at the Chacaltaya cosmic ray laboratory since 2001, and about 100 m² at Koksil, Himalaya, since 2003. It is devoted to the search for intermediate mass magnetic monopoles (10⁷–10¹³ GeV/c²) and nuclearites in the cosmic radiation using stacks of CR-39 and Makrofol nuclear track detectors. In four years of operation it will reach a sensitivity to a flux of about 10^-15 cm^-2 s^-1 sr^-1. We present the results of the calibration of CR-39 and Makrofol and the analysis of a first sample of the exposed detector.     

Is QED inconsistent in the presence of Dirac monopoles?

We examine a recently made claim that an unphysical coupling associated with the longitudinal component of the gauge field appears in the Dirac quantization condition thus rendering QED inconsistent in the presence of Dirac monopoles. We point out that a conventional quantization condition can still be obtained.     

Direct search for Dirac magnetic monopoles in pp collisions at square root s = 1.96 TeV

We search for pair-produced Dirac magnetic monopoles in 35.7 pb(-1) of proton-antiproton collisions at square root s = 1.96 TeV with the Collider Detector at Fermilab (CDF). We find no monopole candidates corresponding to a 95% confidence-level cross-section limit sigma < 0.2 pb for a monopole with mass between 200 and 700 GeV/c2. Assuming a Drell-Yan pair-production mechanism, we set a mass limit m > 360 GeV/c2.     

Dirac monopoles on quantized vortices in superfluid3He

Quantized vortices in superfluid³He display a variety of novel structures that have previously not been observed in any other quantum fluids; their basic experimental manifestations and theoretical features have been reviewed by Hakonen, Lounasmaa and Simola [Physica B160 (1989) 1] and by Salomaa and Volovik [Rev. Mod. Phys.59 (1987) 533]. In order not to repeat these reviews in this paper, here we choose to discuss the theme of the possible pointlike orderparameter singularities, monopoles, that can occur on the quantized³He vortices. Such monopoles, mathematical analogues of the magnetic Dirac monopole, may exist in superfluid³He due to the complicated order-parameter structure, which makes it possible to have several different types of quantized vortex lines and phase boundaries between the superfluid states. Analogs of Dirac monopoles, and also monopoles with 1/2 and 1/4 of the magnetic charge of the Dirac monopole, may exist at the points of intersections of quantized vortex lines and phase boundaries — or along vortices if they change their quantum state; several examples are discussed.Invited talk at the International Conference on Macroscopic Quantum Phenomena, Smolenice Castle, Czechoslovakia, September 18–22, 1989.I want to thank G. E. Volovik for a useful discussion and O. V. Lounasmaa for encouragement. This research has been supported through the Award for the Advancement of European Science by the Körber-Stiftung (Hamburg, FRG) and by the Academy of Finland.     

Quantum field theory of Dirac monopoles and the charge quantization condition

A relativistic quantum field theory of Dirac monopoles in interaction with electric charges is presented. A path-integral quantization is used to discuss the renormalization and derive the Dirac charge quantization condition after higher order effects have been included.     

Dispersion of electromagnetic waves in the presence of magnetic monopoles of electron mass in a uniform magnetic field

The dispersion relation of electromagnetic waves in the presence of magnetic monopoles of electron mass in a uniform magnetic field is obtained. The waves of the frequencyω in the range ω_ϱi<Ω_i<ω<Ω _e <ω_ϱa are analysed. It is shown that the monopole charges lead to observable effects. Finally, the results are applied to a typical pulsar.     

Composite gluons and magnetic monopoles

We present a static solution to the classical field equations of a purely spinorial model with SU(2) internal symmetry. The model contains composite vector and pseudovector gluon fields. The solution for the vector field is precisely that of the Wu-Yang monopole.