No abstract

We review the transformation properties of ELKO spinors (Eigenspinoren des Ladungskonjugationsoperators) under charge conjugation, parity, and time reversal. Our calculations confirm that ELKO spinors are not eigenspinors of the helicity operator and satisfy [Formula: see text] which identifies them as a representation of a nonstandard Wigner class. However, we find that ELKO spinors transform symmetrically under parity instead of the previously assumed asymmetry. Furthermore, we demonstrate that ELKO spinors transform asymmetrically under time reversal, which is opposite to the previously reported symmetric behaviour. These changes affect the (anti)commutation relations that are satisfied by the operators acting on ELKO spinors. We are also able to show that ELKO spinors actually satisfy the same (anti)commutation relations as Dirac spinors, even though they belong to two different representations.

We re-examine collisional annihilation of superheavy dark matter particles in dark matter density spikes in the galactic halo as a possible source of ultrahigh energy cosmic rays. We estimate the possible flux in a way that does not depend on detailed assumptions about the density profiles of dark matter clumps. The result confirms that collisional annihilation is compatible with annihilation cross sections below the unitarity bounds for superheavy dark matter if the particles can form dense cores in dark matter substructure, and it provides estimates for core sizes and densities. The ensuing clumpy source distribution in the galactic halo will be tested within a few years of operation of the Pierre Auger observatory.

We present the derivation of a supersymmetric model for fermionic fields with integer valued mass dimension based on a general superfield with one free spinor index. First, we demonstrate that it is impossible to formulate such a model based on a general scalar superfield. This is due to problems constructing a Lagrangian containing a kinetic term for the fermionic mass dimension one field, as well as problems deriving a consistent second quantisation. We then develop a formalism based on a general superfield with one free spinor index. We systematically derive all associated chiral and anti-chiral superfields up to third order in covariant derivatives. Using this formalism we are able to construct a supersymmetric onshell Lagrangian that contains a kinetic term for the fermionic fields with mass dimension one. We then derive the corresponding on-shell supercurrent and succeed to formulate a consistent second quantisation for the component fields. Finally, we present our result for a supersymmetric Hamiltonian. As the Lagrangian is by construction supersymmetric and the Hamiltonian was derived from the Lagrangian using the supersymmetry algebra the Hamiltonian must be positive definite.

We consider the problem of the evolution of the fine‐structure coefficient α under the assumption that the scalar field coupling to the Maxwell term satisfies the condition mt≫ 1 for coherent dark matter oscillations. In this case we find that the coupling scale f in the leading‐order coupling −(φ/4f) FμνFμν affects the cosmological evolution of α according to ln(α/α0) ∝ξ(mPl/f) × ln [tanh(t/2τ)/tanh(t0/2τ)]. A fit to the QSO observations by Murphy et al. yields f=ξ× 2.12+0.58−0.37× 105mPl. Here mPl= (8πGN)−1/2 is the reduced Planck mass, and ξ2=ϱφ/ϱm parametrizes the contribution of φ to the matter density in the Universe.