International Journal of Modern Physics A

The long-standing conceptual controversies concerning the interpretation of nonrelativistic quantum mechanics are argued, on one hand, to be due to its incompleteness, as affirmed by Einstein. But on the other hand, it appears to be possible to complete it at least partially, as Bohr might have appreciated it, in the framework of its standard mathematical formalism with observables as appropriately defined self-adjoint operators. This completion of quantum mechanics is based on the requirement on laboratory physics to be effectively confined to a bounded space region and on the application of the von Neumann deficiency theorem to properly define a set of self-adjoint extensions of standard observables, e.g. the momenta and the Hamiltonian, in terms of certain isometries on the region boundary. This is formalized mathematically in the setting of a boundary ontology for the so-called Qbox in which the wave function acquires a supplementary dependence on a set of Additional Boundary Variables (ABV). It is argued that a certain geometric subset of the ABV parametrizing Quasi-Periodic Translational Isometries (QPTI) has a particular physical importance by allowing for the definition of an ontic wave function, which has the property of epitomizing the spatial wave function “collapse.” Concomitantly the standard wave function in an unbounded geometry is interpreted as an epistemic wave function, which together with the ontic QPTI wave function gives rise to the notion of two-wave duality, replacing the standard concept of wave-particle duality. More generally, this approach to quantum physics in a bounded geometry provides a novel analytical basis for a better understanding of several conceptual notions of quantum mechanics, including reality, nonlocality, entanglement and Heisenberg’s uncertainty relation. The scope of this analysis may be seen as a foundational update of the multiple versions 1.x of the Copenhagen interpretation of quantum mechanics, which is sufficiently incremental so as to be appropriately characterized as Copenhagen 2.0.

Scalar particles coupled to the Standard Model fields through a disformal coupling arise in different theories, such as massive gravity or braneworld models. We will review the main phenomenology associated with such particles. Distinctive disformal signatures could be measured at colliders and with astrophysical observations. The phenomenological relevance of the disformal coupling demands the introduction of a set of symmetries, which may ensure the stability of these new degrees of freedom. In such a case, they constitute natural dark matter candidates since they are generally massive and weakly coupled. We will illustrate these ideas by paying particular attention to the branon case, since these questions arise naturally in braneworld models with low tension, where they were first discussed.

Form factors are important low-energy quantities and an accurate knowledge of these sheds light on the strong interactions. A variety of methods based on general principles have been developed to use information known in different energy regimes to constrain them in regions where experimental information needs to be tested precisely. Here we review our recent work on the electromagnetic $\omega \pi$ form factor in a model-independent framework known as the method of unitarity bounds, partly motivated by the discrepancies noted recently between the theoretical calculations of the form factor based on dispersion relations and certain experimental data measured from the decay $\omega \to {\pi }^0{\gamma }^{\ast }$. We have applied a modified dispersive formalism, which uses as input the discontinuity of the $\omega \pi$ form factor calculated by unitarity below the $\omega \pi$ threshold and an integral constraint on the square of its modulus above this threshold. The latter constraint was obtained by exploiting unitarity and the positivity of the spectral function of a QCD correlator, computed on the spacelike axis by operator product expansion and perturbative QCD. An alternative constraint is obtained by using data available at higher energies for evaluating an integral of the modulus squared with a suitable weight function. From these conditions we derived upper and lower bounds on the modulus of the $\omega \pi$ form factor in the region below the $\omega \pi$ threshold. The results confirm the existence of a disagreement between dispersion theory and experimental data on the $\omega \pi$ form factor around 0.6 GeV, including those from NA60 published in 2016.

In the light of the Planck 2015 results, we update simple inflationary models based on the quadratic, quartic, Higgs and Coleman–Weinberg potentials in the context of the Randall–Sundrum brane-world cosmology. Brane-world cosmological effect alters the inflationary predictions of the spectral index $(n_s)$ and the tensor-to-scalar ratio $(r)$ from those obtained in the standard cosmology. In particular, the tensor-to-scalar ratio is enhanced in the presence of the 5th dimension. In order to maintain the consistency with the Planck 2015 results for the inflationary predictions in the standard cosmology, we find a lower bound on the five-dimensional Planck mass $(M_5)$. On the other hand, the inflationary predictions laying outside of the Planck allowed region can be pushed into the allowed region by the brane-world cosmological effect with a suitable choice of $M_5$.

In this paper, we analyzed the process of $B_s\to K^{{\mp }^{\ast }}{K}^{\pm }$ decay within QCD factorization (QCDF) and final state interaction (FSI) effects. At first, the $B_s\to K^{{\mp }^{\ast }}{K}^{\pm }$ decay is calculated via QCDF approach. The result that is found by using the QCDF method is less than the experimental result. Then we considered FSI effect as a sizable correction where there are the intermediate state $D_s^{-}{D}_s^{{+}^{\ast }}$ mesons via the exchange of ${\bar{D}}^0({\bar{D}}^{0^{\ast }})$. The experi mental branching ratio of $B_s\to K^{{\mp }^{\ast }}{K}^{\pm }$ decay is $(12.7\pm 1.9)\times 10^{-6}$, and our results by QCDF and FSI are $(2.79\pm 0.08)\times 10^{-6}$ and $(11.6\pm 0.11)\times 10^{-6}$, respectively.

We investigated regular black holes with fuzzy sources in three and four dimensions. The density distributions of such fuzzy sources are inspired by noncommutative geometry and given by Gaussian or generalized Gaussian functions. We utilized mass functions to give a physical interpretation of the horizon formation condition for the black holes. In particular, we investigated three-dimensional BTZ-like black holes and four-dimensional Schwarzschild-like black holes in detail, and found that the number of horizons is related to the space–time dimensions, and the existence of a void in the vicinity of the center of the space–time is significant, rather than noncommutativity. As an application, we considered a three-dimensional black hole with the fuzzy disc which is a disc-shaped region known in the context of noncommutative geometry as a source. We also analyzed a four-dimensional black hole with a source whose density distribution is an extension of the fuzzy disc, and investigated the horizon formation condition for it.

The annihilation of massive scalar particles in one photon in de Sitter expanding universe is studied, using perturbative QED. The amplitude and probability corresponding to this process is computed using the exact solutions of the Klein–Gordon and Maxwell equations on de Sitter geometry. Our results show that the expression of the total probability of photon emission is a function dependent on the ratio mass/expansion factor. We perform a graphical study of the total probability in terms of the parameter mass/expansion factor, showing that this effect is significant only in strong gravitational fields. We also obtain that the total probability for this process vanishes in the Minkowski limit.

We clarify the conditions or assumptions under which theoretical predictions of various models beyond the standard model give mainly in electric dipole moments. The correct interpretation of those conditions seems to be indispensable to the refinements of model building as well as to the mutual reliance in experimental and theoretical communities. The connections of these analyses to the recent experimental results at the LHC and the other places are also discussed.

The interference between resonance signal and continuum background can be either constructive or destructive, depending on the relative sign of couplings between the signal and background amplitudes. Different interference schemes lead to asymmetric distortions of the resonance line shape, which could be distinguished in experiments, when the internal resonance width is larger than the detector resolution. Interpreting the ATLAS diboson excesses by means of a toy $W^{\prime }$ model as an illustrative example (though it is disfavored by the 13 TeV data), we find that the signs of resonance couplings can only be revealed in the line shape measurements up to a high confidence level at a high luminosity, which could bring us further information on the underlying theory beyond resonance searches at future lepton and hadron colliders.

We generalize the Stückelberg holographic superconductor model by including dark matter sector in the five-dimensional AdS soliton space–time beyond the probe limit. We study phase transitions with large charge of the scalar field through the condensation of the scalar operator and the holographic topological entanglement entropy of the system. We find that the entanglement entropy is a good probe of the order of phase transitions and second-order critical phase transition points. By investigating the behaviors of the entanglement entropy, we show that the larger coupling parameter $\alpha$ makes the first-order phase transition more difficult to happen. In all, we conclude that the entanglement entropy can be used to study the effects of the dark matter sector in this general insulator/superconductor system.