Modern Physics Letters A

The GERmanium Detector Array, GERDA, is designed to search for neutrinoless double-beta (0νββ) decay of ⁷⁶Ge and it is installed in the Laboratori Nazionali del Gran Sasso (LNGS) of INFN, Italy. In this review, the detection principle and detector setup of GERDA are described. Also, the main physics results by GERDA Phase I, are discussed. They include the measurement of the half-life of 2νββ decay, the background decomposition of the energy spectrum and the techniques for the discrimination of the background, based on the pulse shape of the signal. In the last part of this review, the estimation of a limit on the half-life of 0νββ ( at 90% C.L.) and the comparison with previous results are discussed. GERDA data from Phase I strongly disfavor the recent claim of 0νββ discovery, based on data from the Heidelberg–Moscow experiment.

Lax representation is elaborated for the equations of motion of massless superparticle on the AdS₄×ℂℙ³ superbackground that proves their classical integrability.

We discuss how a scenario recently proposed for the morphing of macroscopic gravitation into weak interactions at the attometer scale affects our current understanding of high-energy density phenomena. We find that the Yukawa couplings of the fundamental fermions are directly related to their event horizons, setting an upper bound for their observability through gauge interactions. Particles with larger Yukawa couplings are not precluded, but should interact only gravitationally, providing a natural candidate for dark matter. Furthermore, the quantum vacuum contribution to the cosmological constant is reduced by several orders of magnitude with respect to the current estimates. The expected running of the Newtonian gravitational constant could provide a viable alternative scenario to the inflationary stage of the Universe.

We study a new contribution, which is a tree-level transition from long-distance dynamics, to K⁺→π⁺ℓ⁺ℓ^- (ℓ = e, μ) decays. It is found that this tree-diagram can be calculated unambiguously and would generate the additional contribution to the vector, axial-vector, scalar and pseudoscalar form factor of the decay. Our analysis shows that these form factors are strongly suppressed and this long-distance contribution is well under control.

The extended commutation relations for generalized uncertainty principle (GUP) have been based on the assumption of the minimal length in position. Instead of this assumption, we start with a constrained Hamiltonian system described by the conventional Poisson algebra and then impose appropriate second class constraints to this system. Consequently, we can show that the consistent Dirac brackets for this system are nothing, but the extended commutation relations describing the GUP.

We study the classical motion of wiggly strings around a background straight infinitely thin cosmic wiggly string with an electric current along the symmetry axis. The solutions for the wiggly string exhibit open strings lying along the circular orbit.

It is speculated that a possible reason for the scalar mass M_H ≃126 GeV is equality of the lifetimes for vacuum decay and instanton-induced proton decay.

Einstein introduced cosmological constant in his field equations in an ad hoc manner. Cosmological constant plays the role of vacuum energy of the universe which is responsible for the accelerating expansion of the universe. To give a theoretical support, it remains an elusive goal to modern physicists. We provide a prescription to obtain cosmological constant from the phase transitions of the early universe when topological defects, namely monopole might have existed.