Optical absorption for parallel cylinder arrays

We study the long wavelength electromagnetic resonances of interacting cylinder arrays. By using a normal modes expansion where the effects of geometry and material are separated, it is shown that two parallel cylinders with different radii have electromagnetic modes distributed symmetrically about depolarization factor 1/2. Both sets couple to longitudinal and transverse components of the external field, but amplitudes of symmetric depolarization factors become exchanged when considering longitudinal or transverse polarization. We also find that amplitudes satisfy sum rules that depend on the ratio of the cylinders radii.Comment: 14 pages, 3 figure

Outside-in stellar formation in the spiral galaxy M33?

We present and discuss results from chemical evolution models for M33. For our models we adopt a galactic formation with an inside-out scenario. The models are built to reproduce three observational constraints of the M33 disk: the radial distributions of the total baryonic mass, the gas mass, and the O/H abundance. From observations, we find that the total baryonic mass profile in M33 has a double exponential behavior, decreasing exponentially for r<= 6 kpc, and increasing lightly for r > 6 kpc due to the increase of the gas mass surface density. To adopt a concordant set of stellar and H II regions O/H values, we had to correct the latter for the effect of temperature variations and O dust depletion. Our best model shows a good agreement with the observed the radial distributions of: the SFR, the stellar mass, C/H, N/H, Ne/H, Mg/H, Si/H, P/H, S/H, Ar/H, Fe/H,and Z. According to our model, the star formation efficiency is constant in time and space for r <= 6 kpc, but the SFR efficiency decreases with time and galactocentric distance for r > 6 kpc. The reduction of the SFR efficiency occurs earlier at higher r. While the galaxy follows the inside-out formation scenario for all r, the stars follow the inside-out scenario only up to r = 6 kpc, but for r > 6 kpc the stars follow an outside-in formation. The stellar formation histories inferred for each r imply that the average age of the stars for r > 6 increases with r.Comment: Accepted for publication in MNRA

Lagrangian Volume Deformations around Simulated Galaxies

We present a detailed analysis of the local evolution of 206 Lagrangian Volumes (LVs) selected at high redshift around galaxy seeds, identified in a large-volume $\Lambda$ cold dark matter ($\Lambda$CDM) hydrodynamical simulation. The LVs have a mass range of $1 - 1500 \times 10^{10} M_\odot$. We follow the dynamical evolution of the density field inside these initially spherical LVs from $z=10$ up to $z_{\rm low} = 0.05$, witnessing highly non-linear, anisotropic mass rearrangements within them, leading to the emergence of the local cosmic web (CW). These mass arrangements have been analysed in terms of the reduced inertia tensor $I_{ij}^r$, focusing on the evolution of the principal axes of inertia and their corresponding eigendirections, and paying particular attention to the times when the evolution of these two structural elements declines. In addition, mass and component effects along this process have also been investigated. We have found that deformations are led by dark matter dynamics and they transform most of the initially spherical LVs into prolate shapes, i.e. filamentary structures. An analysis of the individual freezing-out time distributions for shapes and eigendirections shows that first most of the LVs fix their three axes of symmetry (like a skeleton) early on, while accretion flows towards them still continue. Very remarkably, we have found that more massive LVs fix their skeleton earlier on than less massive ones. We briefly discuss the astrophysical implications our findings could have, including the galaxy mass-morphology relation and the effects on the galaxy-galaxy merger parameter space, among others.Comment: 23 pages, 20 figures. Minor editorial improvement

The Use of the Military for Law Enforcement Activities in Central America

Faced with the violence, criminality and insecurity now threatening peace and democratic governance in Central America, the region’s governments have decided to use the Armed Forces to carry out actions in response to criminal actions, looking to improve their performance. Although public demand for including the Armed Forces in these functions takes place within a legally legitimate framework, it is motivated by tangible circumstances such as increased levels of violence, delinquency and crime. Despite being coupled with the perception of institutional weakness within the security and judicial system (particularly police) and the recognition of prestige, efficiency, discipline and severity in fulfilling the Armed Forces’ missions, these arguments are insufficient to legitimize the use of the military as a police force. Within this context, this paper reflects on the implications or consequences of the use of the Armed Forces in duties traditionally assigned to the police in the Central American region with the goal of contributing to the debate on this topic taking place in the Americas. To achieve this end, first we will focus on understanding the actual context in which a decision is made to involve the Armed Forces in security duties in the region. Second, we will examine the effects and implications of this decision on the Armed Forces’ relations within their respective societies. Third and finally, considering this is already a reality in the region, this paper will provide recommendations. The main findings of this research, resulting from the application of an analyticaldescriptive and historically based study, are organized in three dimensions: the political dimension, by implication referring to the relationship between the ultimate political authority and the Armed Forces; the social dimension, by implication the opinion of citizens; and other implications not only affecting the structural and cultural organization of armies and police but also the complementary operational framework within a context of comprehensive response by the State. As a main conclusion, it poses there is an environment conducive to the use of the Armed Forces in citizen’s security, in view of the impact of threats provoked by criminal structures of a military nature currently operating in Central America. However, this participation creates an inevitable social and political impact if implemented in isolation or given a political leading role and/or operational autonomy. This participation poses risks to the institutions of the Armed Forces and the police as well. Finally, this paper identifies an urgent need for the Armed Forces’ role to be more clearly defined with regard to security matters, limiting it to threats that impact States’ governability and existence. Nonetheless, Central American States should seek a COMPREHENSIVE response to current crime and violence, using all necessary institutions to confront these challenges, but with defined roles and responsibilities for each and dynamic coordination to complement their actions