相关论文: Helicity Basis for Spin 1/2 and 1
An action with unconventional supersymmetry was introduced in an earlier paper. Here it is shown that this action leads to standard physics for fermions and gauge bosons at low energy, but to testable extensions of standard physics for…
We construct the covariant, spinor sets of relativistic wave equations for a massless field on the basis of the two copies of the R-deformed Heisenberg algebra. For the finite-dimensional representations of the algebra they give a universal…
Proton is a composite particle, so its spin S_P is made from the spins of the partons which the proton consists of. The discrepancy between S_P = 1/2 and the experimentally detected sum of the parton spins was named Proton Spin Puzzle.…
It is argued that spin is a fundamental aspect of gauge theories at short distances. As a consequence there are characteristic helicity asymmetries in hard inclusive and exclusive reactions of which a few are discussed.
An helicity formalism for perturbative calculations is presented. It is based on the formal insertion in spinor lines of a complete set of states built up with unphysical spinors. It is particularly convenient when massive spinors are…
We discuss some recent developments concerning the nucleon's helicity parton distribution functions: New preliminary data from jet production at RHIC suggest for the first time a non-vanishing polarization of gluons in the nucleon. SIDIS…
Helicity is a property of light which is familiar from particle physics but less well-known in optics. In this paper we recall the explicit form taken by the helicity of light within classical electromagnetic theory and reflect upon some of…
Positivity constraints, derived initially assuming parity conservation, for the inclusive reaction of the type $A({spin 1/2})+B({spin 1/2})\to C+X$, where the spins of both initial spin-1/2 particles can be in any possible directions and no…
Different bases for the spin-1 density matrix are discussed to clarify the connection between its components and observables measured in heavy-ion collisions. The theoretical advantage of using the adjoint representation for spin matrices…
We delve into the first principles of quantum field theory to prove that the so-called spin-1/2 ''bosons'' and the fermions with mass dimension 1, including ELKO, cannot represent physical particle states with spin $1/2$. Specifically, we…
Studies of scattering amplitudes for electric and magnetic charges have identified previously overlooked multiparticle representations of the Poincar\'e group in four dimensions. Such representations associate nontrivial quantum numbers…
We formulate part V of a rigorous theory of ground states for classical, finite, Heisenberg spin systems. After recapitulating the central results of the parts I - IV previously published we extend the theory to the case where an involutary…
In this paper the method of the relativistically-invariant effective tensor representation of Lagrangian decomposition and the amplitudes of the two-photon interaction with hadrons on photon energy is proposed. In the frames…
A possibility of an extension of the minimality principle for electromagnetic interactions of charged and neutral particles having spin 1/2 is investigated.
The Bogomolnyi vortex of the N=2 supersymmetric abelian-Higgs model in 2+1 dimensions is shown to be a ``semion'' of spin 1/4. Specifically, the effective superparticle action for one vortex is shown to describe, upon quantization, a parity…
We study the relations between spin squeezing and concurrence, and find that they are qualitatively equivalent for an ensemble of spin-1/2 particles with exchange symmetry and parity, if we adopt the spin squeezing criterion given by the…
We show that under the operation of parity the {\it front-form} $(1/2,\,0)$ and $(0,\,1/2)$ Weyl spinors (massive or massless) do not get interchanged. This has the important consequence that if a front-form theory containing…
We demonstrate that decoherence of many-spin systems can drastically differ from decoherence of single-spin systems. The difference originates at the most basic level, being determined by parity of the central system, i.e. by whether the…
In the ordered phase of a $\mathbb{Z}_2$-symmetric collective spin system, two natural bases -- localised pointer states $\{|P\rangle,|R\rangle\}$ and energy eigenstates $\{|E_0\rangle,|E_1\rangle\}$ -- yield Lindblad dephasing rates that…
Three-point correlators of spinning operators admit multiple tensor structures compatible with conformal symmetry. For conserved currents in three dimensions, we point out that helicity commutes with conformal transformations and we use…