Serious Games for use in a Higher Education Environment.

This paper presents a serious game that covers the teaching of some basic concepts of computer networks, which has been specifically designed for educating university level students. User requirements are collected through an expert user evaluation with academics as well as with a quantitative evaluation with university students. Based on these results, an online serious game was designed and implemented. The effectiveness of the serious game when applied for teaching purposes is quantified through an end-user evaluation with 30 users. Initial evaluation results show that online serious games can be an effective and useful pedagogic tool in teaching computer networks in a higher education environment

Using the Alpha Geodesic Distance in Shapes K-Means Clustering

This paper is based mainly on the relevant work [1]. In that paper the authors studied the problem of clustering of different shapes using Information Geometry tools including, among others, the Fisher Information and the resulting distance. Here we are using the same methods but for the geodesics of the alpha connection for three different values of the alpha parameter

A Nearly Massless Graviton in Einstein-Gauss-Bonnet Inflation with Linear Coupling Implies Constant-roll for the Scalar Field

The striking GW170817 event indicated that the graviton is nearly massless, since the gamma rays emitted from the two neutron stars merging arrived almost simultaneously with the gravitational waves. Thus, the graviton must also be massless during the inflationary and post-inflationary era, since there is no obvious reason to believe otherwise. In this letter we shall investigate the theoretical implications of the constraint that the graviton is massless to an Einstein-Gauss-Bonnet theory with linear coupling of the scalar field to the four dimensional Gauss-Bonnet invariant. As we show, the constraint of having gravitational wave speed of the primordial gravitational waves equal to one, severely restricts the dynamics of the scalar field, imposing a direct constant-roll evolution on it. Also, as we show, the spectral index of the primordial scalar perturbations for the GW170817-compatible Einstein-Gauss-Bonnet theory with linear coupling is different in comparison to the same theory with non-linear coupling. Thus the phenomenology of the model is expected to be different, and we briefly discuss this issue too. In addition, the constant-roll condition is always related to non-Gaussianities, thus it is interesting that the imposition of a massless graviton in an Einstein-Gauss-Bonnet theory with linear coupling may lead to non-Gaussianities, so we briefly discuss this issue too.Comment: EPL Accepte

Constraining the sources of ultra-high energy cosmic rays with multi-messenger data

Ultra-high energy cosmic rays (UHECRs) are cosmic rays with energy exceeding 10¹⁸ electronvolts. The sources of these particles remain unknown despite decades of research. This thesis presents a series of studies aimed at constraining the sources of UHECRs both directly by studying their observed arrival directions and indirectly through their expected secondary gamma-ray signatures. An analysis of the arrival direction distribution of the highest energy cosmic rays detected at the Pierre Auger Observatory is presented. The aim of the study was to determine whether the arrival directions of observed UHECRs follow the distribution of nearby extragalactic sources, which is expected if UHECRs are light nuclei of extragalactic origin. A departure from isotropy at the 95% level is observed but no clear correlation with the extragalactic matter distribution is found. The sensitivity of upcoming UHECR experiments, with an order of magnitude higher annual exposure than current experiments, to the expected UHECR anisotropy has been investigated through simulations. It is shown, that with five years of data from such a detector an anisotropy should be detectable at the 99% level as long as the composition is proton dominated. In a scenario where the UHECR source distribution is strongly clustered, similar to the distribution of galaxy clusters, an anisotropy at the 99.9% level is expected even if the fraction of protons at the highest energies is as low as 30%. Constraints on the sources of UHECRs may also come from the secondary particles that UHECRs produce during their propagation. A study of the expected secondary gamma-ray signatures of UHECR accelerators embedded in magnetised environments is presented. The secondary gamma-ray emission expected in this model is shown to be consistent with the spectra of a number of extreme blazars. It is shown that this model is more robust to variations of the overall extragalactic magnetic eld strength than other proposed scenarios, which is appealing in view of the large uncertainty surrounding the strength and con guration of extragalactic magnetic fi elds