1,365 research outputs found
Relativistic wave equations with fractional derivatives and pseudo-differential operators
The class of the free relativistic covariant equations generated by the
fractional powers of the D'Alambertian operator is studied.
Meanwhile the equations corresponding to n=1 and 2 (Klein-Gordon and Dirac
equations) are local in their nature, the multicomponent equations for
arbitrary n>2 are non-local. It is shown, how the representation of generalized
algebra of Pauli and Dirac matrices looks like and how these matrices are
related to the algebra of SU(n) group. The corresponding representations of the
Poincar\'e group and further symmetry transformations on the obtained equations
are discussed. The construction of the related Green functions is suggested.Comment: 29 pages, Tex. In the corrected version a small bug in
cross-references to some equations is removed. Minor text corrections are
done and some references are adde
Kinematics of deep inelastic scattering in the covariant approach
We study the kinematics of deep inelastic scattering corresponding to the rotationally symmetric distribution of quark momenta in the nucleon rest frame. It is shown that the rotational symmetry together with Lorentz invariance
can impose constraints on the quark intrinsic momenta. Obtained constraints are discussed and compared with the available experimental data
Quark orbital angular momentum: can we learn about it from GPDs and TMDs?
It is known how to access information on quark orbital angular momentum from
generalized parton distribution functions, in a certain specified framework. It
is intuitively expected, that such information can be accessed also through
transverse momentum dependent distribution functions, but not known how. Now
quark models provide promising hints. Recent results are reviewed.Comment: proceeding of the "4th Workshop on Exclusive Reactions at High
Momentum Transfer," 18-21 May 2010, Jefferson La
Parton distribution functions and quark orbital motion
Covariant version of the quark-parton model is studied. Dependence of the
structure functions and parton distributions on the 3D quark intrinsic motion
is discussed. The important role of the quark orbital momentum, which is a
particular case of intrinsic motion, appears as a direct consequence of the
covariant description. Effect of orbital motion is substantial especially for
polarized structure functions. At the same time, the procedure for obtaining
the quark momentum distributions of polarized quarks from the combination of
polarized and unpolarized structure functions is suggested.Comment: 17 pages, 2 figures, 1 table. Paper is accepted for publication in
Eur.Phys.J.
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