Anisotropy of the galaxy cluster X-ray luminosity-temperature relation

We introduce a new test to study the Cosmological Principle with galaxy clusters. Galaxy clusters exhibit a tight correlation between the luminosity and temperature of the X-ray-emitting intracluster medium. While the luminosity measurement depends on cosmological parameters through the luminosity distance, the temperature determination is cosmology-independent. We exploit this property to test the isotropy of the luminosity distance over the full extragalactic sky, through the normalization $a$ of the $L_X-T$ scaling relation and the cosmological parameters $\Omega_m$ and $H_0$. We use two almost independent galaxy cluster samples: the ASCA Cluster Catalog (ACC) and the XMM Cluster Survey (XCS-DR1). Interestingly enough, these two samples appear to have the same pattern for $a$ with respect to the Galactic longitude. We also identify one sky region within $l\sim (-15^o,90^o)$ (Group A) that shares very different best-fit values for $a$ for both samples. We find the deviation of Group A to be $2.7\sigma$ for ACC and $3.1\sigma$ for XCS-DR1. This tension is not relieved after excluding possible outliers or after a redshift conversion to the CMB frame is applied. Using also the HIFLUGCS sample, we show that a possible excess of cool-core clusters in this region, cannot explain the obtained deviations. Moreover, we tested for a dependence of the $L_X-T$ relation on supercluster environment. We indeed find a trend for supercluster members to be underluminous compared to field clusters. However, the fraction of supercluster members is similar in the different sky regions. Constraining $\Omega_m$ and $H_0$ via the redshift evolution of $L_X-T$ and the luminosity distance, we obtain approximately the same deviation amplitudes as for $a$. The observed behavior of $\Omega_m$ for the sky regions that coincide with the CMB dipole is similar to what was found with other cosmological probes as well.Comment: 18 pages, 15 figures, accepted for publication in A&

Hydraluic properties of the mortars at Myriam's Well beach, Tiberias (Israel)

openDurante il periodo 2020-2021, il sito archeologico della spiaggia di Myriam’s Well a Tiberias in Israel è stato scavato dall’Università di Haifa sotto la supervisione del professore Emmanuel Nantet. Il sito consiste in tre struttute che sono state rilevate completamente: l’estensione della mura della città con il molo subacqueo in calcestruzzo a nord della spiaggia, la Struttura Lunga costruita lungo la riva del lago, e le colonne dell’area E. Gli archeologi hanno osservato l’utilizzo di malta idraulica per la costruzione delle mura della città e alcuni tratti murari della Struttura Lunga. L’uso di malta idraulica inizia nel periodo Minoico e Miceneo. L’aggiunta di frammenti ceramici o residui di combustione di origine animale conferiva proprietà idrauliche alle malte, rendendole resistenti all’acqua. La presente ricerca consiste nell’ analisi chimica e mineralogica delle malte provenienti del prolungamento della cinta muraria e dalle pareti della Struttura Lunga, per esaminare le diverse fasi costruttive, le diverse tecniche costruttive e lo sviluppo di fasi idrauliche scarsamente cristalline nelle matrici leganti.During the period 2020-2022, the site at Myriam’s Well beach in Tiberias, Israel, was excavated by the University of Haifa under the supervision of Professor Emmanuel Nantet. The site consists of three structures which have been completely revealed: The extension of the city wall with the concrete pier, which is built underwater in the northern side of the beach., the Long Structure built along the lake shore and the columns in area E. The excavators noticed that hydraulic mortar was used for the construction of the City Wall and some walls of the Long Structure. The use of hydraulic mortar goes back to the prehistoric period and specifically in Minoan and Mycenean time. The addition of ceramic fragments or combustion residues of animal origin gave hydraulic properties to mortars making them resistant against water. This thesis research consists on the chemical and mineralogical analysis of the mortar materials from the extension of the City Wall and the walls of the Long Structure, to examine the different construction phases, several building techniques and the development of the poorly crystalline hydraulic phases in the binder matrices

Stability Properties of 1-Dimensional Hamiltonian Lattices with Non-analytic Potentials

We investigate the local and global dynamics of two 1-Dimensional (1D) Hamiltonian lattices whose inter-particle forces are derived from non-analytic potentials. In particular, we study the dynamics of a model governed by a "graphene-type" force law and one inspired by Hollomon's law describing "work-hardening" effects in certain elastic materials. Our main aim is to show that, although similarities with the analytic case exist, some of the local and global stability properties of non-analytic potentials are very different than those encountered in systems with polynomial interactions, as in the case of 1D Fermi-Pasta-Ulam-Tsingou (FPUT) lattices. Our approach is to study the motion in the neighborhood of simple periodic orbits representing continuations of normal modes of the corresponding linear system, as the number of particles $N$ and the total energy $E$ are increased. We find that the graphene-type model is remarkably stable up to escape energy levels where breakdown is expected, while the Hollomon lattice never breaks, yet is unstable at low energies and only attains stability at energies where the harmonic force becomes dominant. We suggest that, since our results hold for large $N$, it would be interesting to study analogous phenomena in the continuum limit where 1D lattices become strings.Comment: Accepted for publication in the International Journal of Bifurcation and Chao

Inverse design and implementation of a wavelength demultiplexing grating coupler

Nanophotonics has emerged as a powerful tool for manipulating light on chips. Almost all of today's devices, however, have been designed using slow and ineffective brute-force search methods, leading in many cases to limited device performance. In this article, we provide a complete demonstration of our recently proposed inverse design technique, wherein the user specifies design constraints in the form of target fields rather than a dielectric constant profile, and in particular we use this method to demonstrate a new demultiplexing grating. The novel grating, which has not been developed using conventional techniques, accepts a vertical-incident Gaussian beam from a free-space and separates O-band $(1300\mathrm{nm})$ and C-band $(1550\mathrm{nm})$ light into separate waveguides. This inverse design concept is simple and extendable to a broad class of highly compact devices including frequency splitters, mode converters, and spatial mode multiplexers.Comment: 17 pages, 4 figures, 1 table. A supplementary section describing the inverse-design algorithm in detail has been added, in addition to minor corrections and updated reference