Axions and Cosmic Rays

We investigate the propagation of a charged particle in a spatially constant but time dependent pseudoscalar background. Physically this pseudoscalar background could be provided by a relic axion density. The background leads to an explicit breaking of Lorentz invariance; as a consequence processes such as $p\to p \gamma$ or $e\to e \gamma$ are possible within some kinematical constraints. The phenomenon is described by the QED lagrangian extended with a Chern-Simons term that contains a 4-vector which characterizes the breaking of Lorentz invariance induced by the time-dependent background. While the radiation induced (similar to the Cherenkov effect) is too small to influence the propagation of cosmic rays in a significant way, the hypothetical detection of the photons radiated by high energy cosmic rays via this mechanism would provide an indirect way of verifying the cosmological relevance of axions. We discuss on the order of magnitude of the effect.Comment: 16 pages, 3 figures. To appear in Proceedings of the Quarks 2010 International Seminar, Kolomna, Russi

Photon propagation in a cold axion condensate

We discuss some striking properties of photons propagating in a cold axion condensate oscillating coherently in time with a frequency $1/m_a$. Three effects are discussed in this contribution: (a) due to the time dependence of the background, photons moving in the cold axion background have no definite energies and some momenta are not accessible to them. (b) we investigate the combined influence of a magnetic field and the cold axion background and propose a possible interferometric experiment to detect the latter. (c) if the axion condensate has a space dependence, the photon refraction index is modified in the medium, possibly leading to total reflection at the interface with the ordinary vacuum.Comment: 6 pages, 4 figures, to appear in Proceedings of the Patras Workshop 2013, Mainz, June 201

How a cold axion background influences photons

A cold relic axion condensate resulting from vacuum misalignment in the early universe oscillates with a frequency \sim m_a, where m_a is the axion mass. We summarize how the properties of photons propagating in such a medium are modified. Although the effects are small due to the magnitude of the axion-photon coupling, some consequences are striking.Comment: 4 pages, 4 figures. To appear in "Proceedings of the 7th Patras Workshop on Axions, WIMPs and WISPs

Utilidad de la PTH-I intraoperatoria en el diagnóstico precoz de hipocalcemia postiroidectomía total.

Treball Final de Grau en Medicina. Codi: MD1158. Curs acadèmic: 2018/2019.Introduction: In total thyroidectomy, acquired hypoparathyroidism is the most frequent complication, resulting in hypocalcemia. As there is a tendency to an early discharge in these patients, it is intended to obtain reliable markers that allow an early prediction of it. Objectives: The main objective is to determine an intraoperative PTH-i cut-off value as an indicator of risk of hypocalcemia after total thyroidectomy. As secondary objectives, it is intended to compare intra-operative PTH-i with the usual determinations and to calculate its cutt-off values. At the same time, perioperative risk factors related to hypocalcemia are studied. Material and methods: It is an observational, descriptive, transversal and retrospective study. 118 patients were included, who had total thyroidectomy surgery in the Otolaryngology department of the Hospital Universitario de La Plana, from February 2012 to September 2018. Hypoparathyroidism was considered to a PTH-i inferior to 15 pg/mL, and hypocalcemia to the corrected calcium values below 8.5 mg/dL. Results: 21.2% of the patients presented subclinical hypocalcemia and 8.5% symptomatic hypocalcemia. Intra-operative PTH-i does not show a significant association with asymptomatic hypocalcemia, but cases of hyperthyroidism do show significant association with intraoperative PTH-i and with corrected calcemia. The carrying out of Ganglionic drainages was significantly associated with the postoperative PTH-i, after 20 hours of intervention. This is the most specific test to differentiate the normocalcemia pattern from hypocalcemia, and the most sensitive to distinguish if there is clinical hypocalcemia. In ROC curves, the two postoperative determinations, at 20 hours, are the ones which have the largest area under the curve, and therefore the highest diagnostic performance. The cutoff values for PTH-i are 11.55 pg/mL for intraoperative against the 10.6 pg/mL for postoperative operation. Conclusions: The diagnostic test that best predicts hypocalcemia is PTH-i in morning 1, with a cut-off value of 10.6 pg/mL. Intra-operative PTH, has a slightly lower sensitivity and specificity, and therefore can be considered clinically equivalent, but with different cut-off points.Introducción: En la tiroidectomía total, el hipoparatiroidismo adquirido es la complicación más frecuente, dando como resultado una hipocalcemia. Puesto que se tiende al alta precoz en estos pacientes, se pretende obtener marcadores fiables que permitan una predicción temprana del mismo. Objetivos: El objetivo principal es determinar un valor de corte de la PTH-i intraoperatoria como indicador de riesgo de hipocalcemia tras tiroidectomía total. Como objetivos secundarios se pretende comparar la PTH-i intraoperatoria con las determinaciones habituales y calcular sus valores de corte. A la vez, se estudian los factores de riesgo perioperatorios relacionados con la hipocalcemia. Material y métodos: Es un estudio observacional, descriptivo, transversal y retrospectivo. Se incluyeron 118 pacientes intervenidos de tiroidectomía total en el Servicio de Otorrinolaringología del Hospital Universitario de la Plana, en el periodo que comprende desde febrero del año 2012 hasta septiembre del 2018. Se consideró hipoparatiroidismo a una PTH-i inferior a 15 pg/mL, e hipocalcemia a los valores del calcio corregido inferiores a 8,5 mg/dL. Resultados: El 21,2 % de los pacientes presentaron hipocalcemia subclínica y el 8,5% hipocalcemia sintomática. La PTH-i intraoperatoria no muestra una asociación significativa con la hipocalcemia asintomática, pero los casos de hipertiroidismo sí que muestran asociación significativa con la PTH-i intraoperatoria y con la calcemia corregida. Los vaciamientos ganglionares se asocian significativamente con la PTH-i postoperatoria, pasadas 20 horas de la intervención. Esta es la prueba más específica para diferenciar la normocalcemia de la hipocalcemia, y la más sensible para distinguir si existe hipocalcemia clínica. En las curvas ROC, las dos determinaciones postoperatorias, a las 20 horas, son las que mayor área bajo la curva tienen y, por tanto, son las de mayor rendimiento diagnóstico. Los valores de corte para la PTH-i son 11,55 pg/mL para la intraoperatoria frente a los 10,6 pg/mL para la postoperatoria. Conclusiones: La prueba diagnóstica que mejor predice la hipocalcemia es la PTH-i la mañana 1, con un valor corte de 10,6 pg/mL. La PTH-i intraoperatoria, tiene una sensibilidad y especificidad ligeramente inferiores, y por tanto, se pueden considerar equivalentes clínicamente pero con diferentes niveles de corte

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

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

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