We study the scattering of torsional waves through a quasi-one-dimensional cavity both from the experimental and theoretical points of view. The experiment consists of an elastic rod with square cross-section. In order to form a cavity, a notch at a certain distance of one end of the rod was grooved. To absorb the waves, at the other side of the rod, a wedge, covered by an absorbing foam, was machined. In the theoretical description, the scattering matrix S of the torsional waves was obtained. The distribution of S is given by Poisson's kernel. The theoretical predictions show an excellent agreement with the experimental results. This experiment corresponds, in quantum mechanics, to the scattering by a delta potential, in one dimension, located at a certain distance from an impenetrable wall.

We calculate negative moments of the $N$-dimensional Laguerre distribution for the orthogonal, unitary, and symplectic symmetries. These moments correspond to those of the proper delay times, which are needed to determine the statistical fluctuations of several transport properties through classically chaotic cavities, like quantum dots and microwave cavities with ideal coupling

Coherent transport phenomena are difficult to observe due to several sources of decoherence. For instance, in the electronic transport through quantum devices the thermal smearing and dephasing, the latter induced by inelastic scattering by phonons or impurities, destroy phase coherence. In other wave systems, the temperature and dephasing may not destroy the coherence and can then be used to observe the underlying wave behaviour of the coherent phenomena. Here, we observe coherent transmission of mechanical waves through a two-dimensional elastic Sinai billiard with two waveguides. The flexural-wave transmission, performed by non-contact means, shows the quantization when a new mode becomes open. These measurements agree with the theoretical predictions of the simplest model highlighting the universal character of the transmission fluctuations.

The Landauer-Büttiker formalism establishes an equivalence between the electrical conduction through a device, e. g. a quantum dot, and the transmission. Guided by this analogy we perform transmission measurements through three-port microwave graphs with orthogonal, unitary, and symplectic symmetry thus mimicking three-terminal voltage drop devices. One of the ports is placed as input and a second one as output, while a third port is used as a probe. Analytical predictions show good agreement with the measurements in the presence of orthogonal and unitary symmetries, provided that the absorption and the influence of the coupling port are taken into account. The symplectic symmetry is realized in specifically designed graphs mimicking spin 1/2 systems. Again a good agreement between experiment and theory is found. For the symplectic case the results are marginally sensitive to absorption and coupling strength of the port, in contrast to the orthogonal and unitary case. 73.21.Hb, 72.10.Fk Wave transport and wave scattering phenomena have been of great interest in the last decades, both from experimental and theoretical points of view (see for instance Ref.[1]). Apart from the intrinsic importance in the complex scattering in a particular medium, the interest also comes from the equivalence between physical systems belonging to completely different areas, in which the dimensions of the systems may differ by several orders of magnitude [2]. One of these equivalences occurs in mesoscopic quantum systems, where the electrical conduction reduces to a scattering problem through the Landauer-Büttiker formalism [3][4][5]. Following this line, classical analogies of quantum systems have been used as auxiliary tools to understand the properties of the conductance of electronic devices in two-terminal configurations [6][7][8][9][10]. A plethora of chaotic scattering experiments in presence of time reversal invariance (TRI) and no spin 1/2 have been performed [7,8,[10][11][12][13][14][15][16], while very few experimental studies regarding absence of TRI are reported [7,8,17,18]. Furthermore, due to its intrinsic complexity, there are no scattering experiments up to now for systems with TRI and spin 1/2, where the signatures of the symplectic ensemble are expected, though there is one study of the spectral statistics in Au nanoparticles obeying this symmetry [19]. Moreover, very recently the appearance of a microwave experiment showing the signatures of the symplectic symmetry [20,21] for eigenvalue statistics has opened the possibility to study transport in the presence of this symmetry.Multiterminal devices are good candidates to provide experimental realizations for the three symmetry classes: Device Terminal 1 Terminal 2 Terminal 3 Junction FIG. 1. Sketch of a three-terminal setting that allows the measurement of the voltage along a device. The device carries a current while the vertical wire measures the voltage drop. Thin lines represent perfect conductors connected to sources of voltages V1, V2, and V3.orthogonal, un...

We study the scattering of waves in systems with losses or gains simulated by imaginary potentials. This is done for a complex delta potential that corresponds to a spatially localized absorption or amplification. In the Argand plane the scattering matrix moves on a circle C centered on the real axis, but not at the origin, that is tangent to the unit circle. From the numerical simulations it is concluded that the distribution of the scattering matrix, when measured from the center of the circle C, agrees with the nonunitary Poisson kernel. This result is also obtained analytically by extending the analyticity condition, of unitary scattering matrices, to the no-unitary ones. We use this nonunitary Poisson kernel to obtain the distribution of nonunitary scattering matrices when measured from the origin of the Argand plane. The obtained marginal distributions have excellent agreement with the numerical results.