Gravity and handedness of photons

Vacuum fluctuations of quantum fields are altered in presence of a strong gravitational background, with important physical consequences. We argue that a non-trivial spacetime geometry can act as an optically active medium for quantum electromagnetic radiation, in such a way that the state of polarization of radiation changes in time, even in the absence of electromagnetic sources. This is a quantum effect, and is a consequence of an anomaly related to the classical invariance under electric-magnetic duality rotations in Maxwell theory.Comment: First Award in the 2017 Essay Competition of the Gravity Research Foundatio

Classical and quantum aspects of electric-magnetic duality rotations in curved spacetimes

It is well known that the source-free Maxwell equations are invariant under electric-magnetic duality rotations, F --> F cos {\theta} + *F sin {\theta}. These transformations are indeed a symmetry of the theory in Noether sense. The associated constant of motion is the difference in the intensity between self- and anti-self dual components of the electromagnetic field or, equivalently, the difference between the right and left circularly polarized components. This conservation law holds even if the electromagnetic field interacts with an arbitrary classical gravitational background. After re-examining these results, we discuss whether this symmetry is maintained when the electromagnetic field is quantized. The answer is in the affirmative in the absence of gravity, but not necessarily otherwise. As a consequence, the net polarization of the quantum electromagnetic field fails to be conserved in curved spacetimes. This is a quantum effect, and it can be understood as the generalization of the fermion chiral anomaly to fields of spin one

On the Electric-Magnetic Duality Symmetry: Quantum Anomaly, Optical Helicity, and Particle Creation

It is well known that not every symmetry of a classical field theory is also a symmetry of its quantum version. When this occurs, we speak of quantum anomalies. The existence of anomalies imply that some classical Noether charges are no longer conserved in the quantum theory. In this paper, we discuss a new example for quantum electromagnetic fields propagating in the presence of gravity. We argue that the symmetry under electric-magnetic duality rotations of the source-free Maxwell action is anomalous in curved spacetimes. The classical Noether charge associated with these transformations accounts for the net circular polarization or the optical helicity of the electromagnetic field. Therefore, our results describe the way the spacetime curvature changes the helicity of photons and opens the possibility of extracting information from strong gravitational fields through the observation of the polarization of photons. We also argue that the physical consequences of this anomaly can be understood in terms of the asymmetric quantum creation of photons by the gravitational~field.Comment: 15 page

Electromagnetic Duality Anomaly in Curved Spacetimes

The source-free Maxwell action is invariant under electric-magnetic duality rotations in arbitrary spacetimes. This leads to a conserved classical Noether charge. We show that this conservation law is broken at the quantum level in the presence of a background classical gravitational field with a nontrivial Chern-Pontryagin invariant, in parallel with the chiral anomaly for massless Dirac fermions. Among the physical consequences, the net polarization of the quantum electromagnetic field is not conserved

Waste volume estimation tool for optimizing construction and demolition waste management in railway works

The increase of construction and demolition (C&D) waste generation has raised new regulations for C&D waste prevention among the European countries, including the obligation to quantify the C&D waste expected to be generated during construction works. This has led to the development of many research works. However, almost none regarding civil engineering works. Therefore, the aim of this research study is to provide a C&D waste estimation tool for railway works. For this purpose several Spanish railway roads have been analyzed in order to develop an equation to estimate in advance the volume of C&D waste likely to be generated, analyzing the category of C&D waste generated for each of the functional units considered. From the analysis performed it has been proved a relationship between the amount of C&D waste generated and the functional units of railways. In short, the methodology presented can help in assigning an optimal and systematic management of the C&D waste produced and assist the construction agents in developing the waste management plans according to the existing legislation

Spontaneous creation of circularly polarized photons in chiral astrophysical systems

This work establishes a relation between chiral anomalies in curved spacetimes and the radiative content of the gravitational field. In particular, we show that a flux of circularly polarized gravitational waves triggers the spontaneous creation of photons with net circular polarization from the quantum vacuum. Using waveform catalogues we identify precessing binary black holes as astrophysical configurations that emit such gravitational radiation, and then solve the fully non-linear Einstein's equations with numerical relativity to evaluate the net effect. The quantum amplitude for a merger is comparable to the Hawking emission rate of the final black hole, and small to be directly observed. However, the implications for the inspiral of binary neutron stars could be more prominent, as argued on symmetry grounds.Comment: 7 pages, 3 figure

Abating the Feminization of Poverty: Changing the Rules Governing Post - Decree Modification of Child Support Obligations

El crecimiento estimado para el mercado mundial de espacios de coworking será de 17% para el año 2020, respecto del año anterior (Desmag, 2018), lo cual muestra el dinamismo de esta nueva forma de trabajar a nivel mundial. En el 2013 se registró la primera empresa de coworking en el Perú denominada Comunal, luego ingresaron al mercado otras marcas internacionales y locales. El punto en común entre todas las opciones actuales es que sus modelos de negocios están enfocados en generar comodidad, modernidad y ahorro a sus arrendatarios.  El presente Plan de Negocios tiene como objetivo desarrollar una nueva propuesta de espacios compartidos, denominada Prime Coworking. Este espacio generará ahorro a emprendedores, pequeñas y medianas empresas, siguiendo las tendencias locales e internacionales. Esto se logrará ofreciendo ambientes cómodos, modernos e implementados para la actividad empresarial, y sobre todo que contribuyan a incentivar la retención de sus trabajadores mediante capacitaciones en habilidades blandas. Por último, con la evaluación del proyecto se concluye que el negocio es viable, dado que para una inversión total de 1 007 160 soles se genera un valor actual neto de 338 mil soles. La inversión será financiada con un aporte de los socios de 705 010 soles que generará un valor para el accionista de 311 000 soles, para un periodo de valoración de 5 años y con un payback de 3.6 años.Coworking spaces global market growth is estimated to be 17% YoY by 2020, (Desmag, 2018), which shows the increasing demand for this new way of working worldwide. In 2013, the first coworking company in Peru called Comunal was registered, then other international and local brands entered the local market. The common point among all market competitors is that their business models are focused on generating comfort, a trendy style and operating savings to their tenants. This Business Plan aims to develop a new proposal for shared spaces, called Prime Coworking, that follows local and international trends and generates savings to entrepreneurs, small and medium enterprises. It does this by offering comfortable, modern and fully implemented environments for doing business and especially by encouraging the engagement of their employees through training in soft skills. Lastly, after our project evaluation it is concluded that the business is profitable, given a total investment of 1 007 160 soles, and an NPV of 338 thousand soles. This investment will be financed with equity of 705 010 soles in shares that will generate a shareholder value of 311 000 soles, for a period of 5 years with a payback of 3.6 years.Trabajo de investigació