Quantization of the elastic modes in an isotropic plate

We quantize the elastic modes in a plate. For this, we find a complete, orthogonal set of eigenfunctions of the elastic equations and we normalize them. These are the phonon modes in the plate and their specific forms and dispersion relations are manifested in low temperature experiments in ultra-thin membranes.Comment: 14 pages, 2 figure

THE INFLUENCE OF FLUVIAL DYNAMICS ON GEOARCHAEOSITES FROM THE DANUBE BANK (THE MĂCIN BRANCH). CASE STUDY: TROESMIS FORTRESS (ROMANIA)

The influence of fluvial dynamics on geoarchaeosites from the Danube Bank (the Măcin Branch). Case study: Troesmis Fortress (Romania). Built since the first century AD, the fortresses along the right bank of the Danube river have suffered decay along the ages as a result of anthropic and geomorphological factors (weathering of construction rocks, fluvial and eolian erosion). Therefore, in order to study the evolution of the sites, analysis of the geological, geomorphological, hydrological and climatic conditions were made. Our study aims to analyze the Troesmis Geto-Dacian site (III - IV century AD) situated on the right bank of the Măcin Branch. Nowadays, the fortress stage of degradation is quite advanced, the main natural decay favouring factor being lateral erosion from the Danube. Fluvial erosion and associated geomorphological processes have determined the retreat of the right bank of the Danube, which led to the structural destruction of the archaeological sites. In order to determine the fluvial dynamics of the Măcin Branch sector, bibliographic materials (maps from different time periods etc) were analyzed and field observations were made. The result consisted mainly in the creation of maps that presents the dynamic of the Măcin Branch (Danube) and its influence on the Troesmis geoarchaeosite

Interaction of Lamb modes with two-level systems in amorphous nanoscopic membranes

Using a generalized model of interaction between a two-level system (TLS) and an arbitrary deformation of the material, we calculate the interaction of Lamb modes with TLSs in amorphous nanoscopic membranes. We compare the mean free paths of the Lamb modes with different symmetries and calculate the heat conductivity $\kappa$. In the limit of an infinitely wide membrane, the heat conductivity is divergent. Nevertheless, the finite size of the membrane imposes a lower cut-off for the phonons frequencies, which leads to the temperature dependence $\kappa\propto T(a+b\ln T)$. This temperature dependence is a hallmark of the TLS-limited heat conductance at low temperature.Comment: 9 pages, 2 figure

Heat transport in ultra-thin dielectric membranes and bridges

Phonon modes and their dispersion relations in ultrathin homogenous dielectric membranes are calculated using elasticity theory. The approach differs from the previous ones by a rigorous account of the effect of the film surfaces on the modes with different polarizations. We compute the heat capacity of membranes and the heat conductivity of narrow bridges cut out of such membranes, in a temperature range where the dimensions have a strong influence on the results. In the high temperature regime we recover the three-dimensional bulk results. However, in the low temperature limit the heat capacity, $C_V$, is proportional with $T$ (temperature), while the heat conductivity, $\kappa$, of narrow bridges is proportional to $T^{3/2}$, leading to a thermal cut-off frequency $f_c=\kappa/C_V\propto T^{1/2}$.Comment: 6 pages and 6 figure

Non-equilibrium Landauer Transport Model for Hawking radiation from a Black Hole

We propose that the Hawking radiation energy and entropy flow rates from a black hole can be viewed as a one-dimensional (1D), non-equilibrium Landauer transport process. Support for this viewpoint comes from previous calculations invoking conformal symmetry in the near-horizon region, which give radiation rates that are identical to those of a single 1D quantum channel connected to a thermal reservoir at the Hawking temperature. The Landauer approach shows in a direct way the particle statistics independence of the energy and entropy fluxes of a black hole radiating into vacuum, as well as one near thermal equilibrium with its environment. As an application of the Landauer approach, we show that Hawking radiation gives a net entropy production that is 50% larger than that obtained assuming standard three-dimensional emission into vacuum.Comment: 14 pages, 2 figures, published versio