Some theoretical and experimental aspects of axion physics

In this thesis we study axions, a byproduct of the Peccei-Quinn solution to the strong CP problem, which are also a viable candidate for the dark matter content of the Universe. In the first part of the thesis, we revisit the Dine-Fischler-Srednicki-Zhitnisky axion model in light of the recent Higgs LHC results and electroweak precision data. This model is an extension of the two-Higgs-doublet model incorporating a PQ symmetry which leads to a physically acceptable axion. For generic values of the couplings, the model reproduces the minimal Standard Model, with a massless axion and all the other degrees of freedom at a very high scale. However, in some scenarios, the extra Higgses could be relatively light. We use the oblique corrections, in particular Δρ, to constrain the mass spectrum in this case. Finally, we also work out the non-linear parametrization of the DFSZ model in the generic case where all scalars except the lightest Higgs and the axion have masses at or beyond the TeV scale. In the second part, we study the relevance of a cold axion background (CAB) as a responsible for the dark matter in the Universe. We examine indirect consequences of its presence through its effects on photon and cosmic ray propagation. First, we study the axion-photon system under the joint influence of two backgrounds: an external magnetic field and a CAB. Their effect consists in producing a three-way mixing of the axion with the two polarizations of the photon. We determine the proper frequencies and eigenvectors as well as the corresponding photon ellipticity and induced rotation of the polarization plane that depend both on the magnetic field and the local density of axions. We also comment on the possibility that some of the predicted effects could be measured in optical table-top experiments. Then, we consider the case in which no magnetic field is present. Here, circularly polarized photons are energy eigenstates, with a modified dispersion relation. This enables the emission of a photon by a charged particle, such as a cosmic ray, which is forbidden in regular QED due to energy-momentum conservation. We study the energy loss of a cosmic ray due to this process and compute the energy flux of photons emitted in this way, which depends on the cosmic ray spectrum

Some theoretical and experimental aspects of axion physics

[eng] In this thesis we study axions, a byproduct of the Peccei-Quinn solution to the strong CP problem, which are also a viable candidate for the dark matter content of the Universe. In the first part of the thesis, we revisit the Dine-Fischler-Srednicki-Zhitnisky axion model in light of the recent Higgs LHC results and electroweak precision data. This model is an extension of the two-Higgs-doublet model incorporating a PQ symmetry which leads to a physically acceptable axion. For generic values of the couplings, the model reproduces the minimal Standard Model, with a massless axion and all the other degrees of freedom at a very high scale. However, in some scenarios, the extra Higgses could be relatively light. We use the oblique corrections, in particular Δρ, to constrain the mass spectrum in this case. Finally, we also work out the non-linear parametrization of the DFSZ model in the generic case where all scalars except the lightest Higgs and the axion have masses at or beyond the TeV scale. In the second part, we study the relevance of a cold axion background (CAB) as a responsible for the dark matter in the Universe. We examine indirect consequences of its presence through its effects on photon and cosmic ray propagation. First, we study the axion-photon system under the joint influence of two backgrounds: an external magnetic field and a CAB. Their effect consists in producing a three-way mixing of the axion with the two polarizations of the photon. We determine the proper frequencies and eigenvectors as well as the corresponding photon ellipticity and induced rotation of the polarization plane that depend both on the magnetic field and the local density of axions. We also comment on the possibility that some of the predicted effects could be measured in optical table-top experiments. Then, we consider the case in which no magnetic field is present. Here, circularly polarized photons are energy eigenstates, with a modified dispersion relation. This enables the emission of a photon by a charged particle, such as a cosmic ray, which is forbidden in regular QED due to energy-momentum conservation. We study the energy loss of a cosmic ray due to this process and compute the energy flux of photons emitted in this way, which depends on the cosmic ray spectrum

Photons in a cold axion background and strong magnetic fields: Polarimetric consequences

In this work we analyze the propagation of photons in an environment where a strong magnetic field (perpendicular to the photon momenta) coexists with an oscillating cold axion background with the characteristics expected from dark matter in the galactic halo. Qualitatively, the main effect of the combined background is to produce a three-way mixing among the two photon polarizations and the axion. It is interesting to note that in spite of the extremely weak interaction of photons with the cold axion background, its effects compete with those coming from the magnetic field in some regions of the parameter space. We determine (with one plausible simplification) the proper frequencies and eigenvectors as well as the corresponding photon ellipticity and induced rotation of the polarization plane that depend both on the magnetic field and the local density of axions. We also comment on the possibility that some of the predicted effects could be measured in optical table-top experiments

Axion-Higgs interplay in the two-Higgs-doublet model

he Zhitnitsky and Dine, Fischler and Srednicki (DFSZ) model is a natural extension of the two-Higgs-doublet model containing an additional singlet, endowed with a Peccei-Quinn symmetry, and leading to a physically acceptable axion. In this paper we reexamine this model in the light of some new developments. For generic couplings the model reproduces the minimal Standard Model showing only tiny deviations (extreme decoupling scenario) and all additional degrees of freedom (with the exception of the axion) are very heavy. Recently it has been remarked that the limit where the coupling between the singlet and the two doublets becomes very small is technically natural. Combining this limit with the requirement of exact or approximate custodial symmetry, we may obtain an additional 0+ Higgs at the weak scale, accompanied by relatively light charged and neutral pseudoscalars. The mass spectrum would then resemble that of a generic two-Higgs-doublet model, with naturally adjustable masses in spite of the large scale that the axion introduces. However, the couplings are nongeneric in this model. We use the recent constraints derived from the Higgs-WW coupling together with oblique corrections to constrain the model as much as possible. As an additional result, we work out the nonlinear parametrization of the DFSZ model in the generic case where all scalars except the lightest Higgs and the axion have masses at or beyond the TeV scale

{'en_US': 'Sexual dysfunction and quality of life depending on the type of renal replacement therapy', 'es_ES': 'Disfunción sexual y calidad de vida según el tipo de tratamiento renal sustitutivo'}

Se precisan estudios que evalúen el impacto de las distintas modalidades de tratamiento renal sustitutivo en referencia a su calidad de vida y disfunción sexual. Objetivos: Evaluar la calidad de vida y la esfera sexual medidas por el cuestionario validado KDQOL-SFTM entre tres grupos de pacientes. Material y métodos: Estudio observacional trasversal comparativo. Se estudiaron 72 pacientes 22,2% de peritoneal, 65,3% de hemodiálisis y 12,5% de domiciliaria. Resultados: El 29,7% de los pacientes en hemodiálisis consideran que la enfermedad renal crónica afectó "muchísimo" y "mucho" a su vida sexual. El 55,4% de los pacientes en hemodiálisis admite problemas para disfrutar de la actividad sexual frente al 62,5% en peritoneal y 44,4% en domiciliaria. Conclusiones: Los pacientes domiciliarios son los que presentan menor impacto sobre la esfera sexual

Disfunción sexual y calidad de vida según el tipo de tratamiento renal sustitutivo

Se precisan estudios que evalúen el impacto de las distintas modalidades de tratamiento renal sustitutivo en referencia a su calidad de vida y disfunción sexual. Objetivos: Evaluar la calidad de vida y la esfera sexual medidas por el cuestionario validado KDQOL-SF TM entre tres grupos de pacientes. Material y métodos: Estudio observacional trasversal comparativo. Se estudiaron 72 pacientes 22,2% de peritoneal, 65,3% de hemodiálisis y 12,5% de domiciliaria. Resultados: El 29,7% de los pacientes en hemodiálisis consideran que la enfermedad renal crónica afectó "muchísimo" y "mucho" a su vida sexual. El 55,4% de los pacientes en hemodiálisis admite problemas para disfrutar de la actividad sexual frente al 62,5% en peritoneal y 44,4% en domiciliaria. Conclusiones: Los pacientes domiciliarios son los que presentan menor impacto sobre la esfera sexual