Isotropy theorem for cosmological Yang-Mills theories

We consider homogeneous non-abelian vector fields with general potential terms in an expanding universe. We find a mechanical analogy with a system of N interacting particles (with N the dimension of the gauge group) moving in three dimensions under the action of a central potential. In the case of bounded and rapid evolution compared to the rate of expansion, we show by making use of a generalization of the virial theorem that for arbitrary potential and polarization pattern, the average energy-momentum tensor is always diagonal and isotropic despite the intrinsic anisotropic evolution of the vector field. We consider also the case in which a gauge-fixing term is introduced in the action and show that the average equation of state does not depend on such a term. Finally, we extend the results to arbitrary background geometries and show that the average energy-momentum tensor of a rapidly evolving Yang-Mills fields is always isotropic and has the perfect fluid form for any locally inertial observer.Comment: 8 pages, 3 figure

Isotropy theorem for arbitrary-spin cosmological fields

We show that the energy-momentum tensor of homogeneous fields of arbitrary spin in an expanding universe is always isotropic in average provided the fields remain bounded and evolve rapidly compared to the rate of expansion. An analytic expression for the average equation of state is obtained for Lagrangians with generic power-law kinetic and potential terms. As an example we consider the behavior of a spin-two field in the standard Fierz-Pauli theory of massive gravity. The results can be extended to general space-time geometries for locally inertial observers.Comment: 4 pages, 0 figures. Published on JCA

Cosmological perturbations in coherent oscillating scalar field models

The fact that fast oscillating homogeneous scalar fields behave as perfect fluids in average and their intrinsic isotropy have made these models very fruitful in cosmology. In this work we will analyse the perturbations dynamics in these theories assuming general power law potentials $V(\phi)=\lambda \vert\phi\vert^{n}/n$. At leading order in the wavenumber expansion, a simple expression for the effective sound speed of perturbations is obtained $c_{\text{eff}}^2 = \omega=(n-2)/(n+2)$ with $\omega$ the effective equation of state. We also obtain the first order correction in $k^2/\omega_{\text{eff}}^2$, when the wavenumber $k$ of the perturbations is much smaller than the background oscillation frequency, $\omega_{\text{eff}}$. For the standard massive case we have also analysed general anharmonic contributions to the effective sound speed. These results are reached through a perturbed version of the generalized virial theorem and also studying the exact system both in the super-Hubble limit, deriving the natural ansatz for $\delta\phi$; and for sub-Hubble modes, exploiting Floquet's theorem.Comment: 13 pages, 6 figures. Published on JHE

Study of Materials and Adhesives for Superconducting Cable Feedthroughs

Powering superconducting magnets requires the use of cryogenic feedthroughs for the superconducting cables capable of withstanding severe thermal, mechanical and electrical operating conditions. Such feedthrough shall provide the continuity of the superconducting circuit while ensuring a hydraulic separation at cryogenic temperature. A study about the adhesive and polymers required for the production of thermal shock resistant feedthroughs is presented. The strength of the busbar to adhesive joints was first investigated by compression/shear tests as well as pin and collar tests performed with four epoxy adhesives. After the selection of the most appropriate adhesive, pin and collar tests were performed with four different polymers. Based on the results, a superconducting cable feedthrough for 6 busbars of 6 kA and 12 busbars of 120 A was constructed and successfully tested

Unsupervised Learning for the Analysis and Detection of Fraud in the Insurance Industry

[EN] Analysis and detection of fraud in the insurance sector has traditionally been carried out through supervised learning. The main problem is that the data presents a strong imbalance and techniques are used to balance the variable. Unsupervised learning is an alternative to consider, especially anomaly detection methodologies. If the fraud variable has a significant imbalance, then it can be treated as an anomaly. That is, the behavior of the fraudsters must be different from the rest of the insured.The main methodologies used are Isolation Forest, Attribute wise learning for scoring outliers (ALSO), Trimmed K-means, Autoencoders (neural networks) and Principal Component Analysis. The objective is through dimensionality reduction techniques to obtain a model with which to make predictions. The instances that present greater differences between the real values and the values estimated with this methodology will be considered anomalies and analyzed as if they were fraud.The results obtained show that these methodologies can be used as a complement to supervised learning. The assembly of models will allow the integration of both methodologies and improve the detection of fraud in the insurance sector.Alvarez-Jareño, JA.; Pavía, JM. (2022). Unsupervised Learning for the Analysis and Detection of Fraud in the Insurance Industry. En 4th International Conference on Advanced Research Methods and Analytics (CARMA 2022). Editorial Universitat Politècnica de València. 279-279. http://hdl.handle.net/10251/18970627927

Constraints on anharmonic corrections of Fuzzy Dark Matter

The cold dark matter (CDM) scenario has proved successful in cosmology. However, we lack a fundamental understanding of its microscopic nature. Moreover, the apparent disagreement between CDM predictions and subgalactic-structure observations has prompted the debate about its behaviour at small scales. These problems could be alleviated if the dark matter is composed of ultralight fields $m \sim 10^{-22}\ \text{eV}$, usually known as fuzzy dark matter (FDM). Some specific models, with axion-like potentials, have been thoroughly studied and are collectively referred to as ultralight axions (ULAs) or axion-like particles (ALPs). In this work we consider anharmonic corrections to the mass term coming from a repulsive quartic self-interaction. Whenever this anharmonic term dominates, the field behaves as radiation instead of cold matter, modifying the time of matter-radiation equality. Additionally, even for high masses, i.e. masses that reproduce the cold matter behaviour, the presence of anharmonic terms introduce a cut-off in the matter power spectrum through its contribution to the sound speed. We analyze the model and derive constraints using a modified version of CLASS and comparing with CMB and large-scale structure data.Comment: 14 pages, 7 figure

Characterization fo the molecular mechanism of action of a new inhibitor of the complex cyclin-dependent kinase 2-cyclin A

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Avian predators as a biological control system of common vole (Microtus arvalis) populations in NW Spain: experimental set-up and preliminary results

Jareño, D., Paz, A., Arroyo, L., Viñuela, J., Arroyo, B.E., Mougeot, F., Luque-Larena, J.J., Fargallo, J.A