International Journal of Modern Physics A

The Superheated Instrument for Massive ParticLe searches (SIMPLE) consists of an astroparticle dark matter search experiment with large active mass superheated droplet detectors (SDDs), that are installed at the underground low noise laboratory in France (LSBB). Several factors made the use of SDDs an attractive approach for the detection of weakly interacting massive particles (WIMPs), namely their intrinsic insensitivity to minimally ionizing particles, high fluorine content, low cost and operation at near ambient pressure and temperature. The signal that arises from the droplet phase transition generates a millimetric-sized gas bubble that is recorded by acoustic means. I describe the SIMPLE detectors, their acoustic instrumentation and signal analysis, which generated several science measurements executed through several phases over the last 20 years: the Pilot Phase with an exposure of 0.19 kgd, Phase I with an exposure of 0.42 kgd, Phase II with an exposure of 18.24 kgd and, an intended Phase III with an expected exposure increasing from 100 to 2500 kgd to be executed with a bubble chamber.

In the context of modified $f({𝒢})=\alpha {{𝒢}}^n+\beta {𝒢}ln({𝒢})$ gravity model, the current study highlights the effect of electric charge for static spherically symmetric stellar models in presence of anisotropic matter distribution. For this purpose, we specifically consider the metric potentials of Tolman–Kuchowicz space–time, which are singularity free and satisfy the stability criteria. The possible existence of charge and a strong electric field, inside the stars is due to the higher values of energy density of matter, pressure distribution and gravitational fields. For the solution of Einstein–Maxwell field equations, the simplified phenomenological MIT bag equation of state, i.e. $p_r=\frac{1}{3}(\rho -4Bg)$ and a specific form of electrical charge distribution $q(r)=Q{\left(\frac{r}{R}\right)}^3=\mathrm{\Psi }{r}^3$ are to be considered. Further, to derive the values of unknown parameters of the stellar objects, we match interior Tolman–Kuchowicz space–time to exterior Reissner–Nordström metric, at the surface of stellar system. In addition to this, for the physical validity and stability of our suggested model, we conduct several physical tests such as effective energy density, effective pressures, energy conditions, stability against equilibrium of the forces, mass-radius relation, surface redshift, Herrera’s cracking concept and electric charge for well-known compact stellar objects viz., SAX J 1808.4-3658 and PSR 1937+21. It is observed that all these tests follow the physically accepted pattern and the influence of charge leads to more stable and viable stellar structures of compact objects in $f({𝒢})$ gravity.

The description of the electromagnetic interaction of charged spinless particles is usually formulated by the Scalar Quantum Electrodynamics. However, there is an alternative formulation given by the Duffin–Kemmer–Petiau theory: the Scalar DKP gauge theory. The proof of the equivalence between these two formulations has been discussed in many researches, but there is not yet a conclusive proof. In this paper, we initiate a complete proof in the framework of the Causal Perturbation theory, showing that both scalar formulations provide the same results for the differential cross-section at tree level.

The bumblebee field coupled with gravity is considered. This gravitational theory exhibits spontaneous breaking of Lorentz symmetry. The Gödel-type universe is introduced and then the causality and its violation are studied. Causal and noncausal Gödel-type solutions are obtained for different content of matter. In addition, when the coupling constant, which controls the interaction between the bumblebee field and the gravitational field, is zero the bumblebee potential may be associated with the value of the cosmological constant of the general relativity. Furthermore, the case with the nonzero coupling constant is also investigated.

In this paper, we investigate the special properties of geometrical particles with null paths in de Sitter 3-space–time, new Frenet equations and an important invariant associated with null paths are presented. By means of unfolding theory, the local topological structure of the lightlike dual surfaces is revealed. It is found that the lightlike dual surface has some singularities whose types can be determined by the invariant. Based on the theory of Legendrian dualities on pseudospheres and the theory of contact manifolds, it is shown that there exists the ${\mathrm{\Delta }}_4$-dual relationship between the lightlike transversal trajectory of the particle and the lightlike dual surface. In addition, an interesting and important fact mentioned is that the contact of lightlike transversal trajectory with lightcone quadric and the contact of lightlike transversal trajectory with null hyperplane have the same order when they are related to the same type of singularities of the lightlike dual surface.

In the LHC era the issue of the origin and nature of neutrino mass has attained a new meaning and a renewed importance. The growing success of the Higgs–Weinberg mechanism behind the charged fermion masses paves the way for answering the question of neutrino mass. We have shown recently how the spontaneous breaking of parity in the context of the minimal left–right symmetric model allows to probe the origin of neutrino mass in complete analogy with the charged fermions masses in the Standard Model. We revisit here this issue and fill in the gaps left in our previous work. In particular we discuss a number of different mathematical approaches to the problem of disentangling the seesaw mechanism and show how a unique analytical solution emerges. Most important, we give all the possible expressions for the neutrino Dirac mass matrix for general values of light and heavy neutrino mass matrices. In practical terms what is achieved is an untangling of the seesaw mechanism with clear and precise predictions testable at hadron colliders such as LHC.