Proximity Effects and Quantum Dissipation in the Chains of YBa2_2Cu3_3O$_{6+x}

We argue that the results of recent scanning tunneling microscopy, angle-resolved photoemission and infrared spectroscopy experiments on the CuO chains of YBa$_2$Cu$_3$O$_{6+x}$ are consistently explained within a proximity model by the interplay of a coherent chain-plane and an incoherent interchain coupling. We show that the CuO$_2$ planes act as an ohmic heat bath for the electronic degrees of freedom in the chains which induces a substantial quantum dissipation. Below the planar $T_c$, charge excitations in the chains acquire a universal superconducting gap whose phase and magnitude are momentum dependent. We predict that the magnitude of this gap varies non-monotonically with the hole concentration in the chains.Comment: 5 pages, 4 figure

Electronic Raman Scattering in Superconducting Cuprates

We show that the novel features observed in Raman experiments on optimally doped and underdoped Bi-2212 compounds in $B_{1g}$ geometry can be explained by a strong fermionic self-energy due to the interaction with spin fluctuations. We compute the Raman intensity $R(\omega)$ both above and below $T_c$, and show that in both cases $R(\omega)$ progressively deviates, with decreasing doping, from that in a Fermi-gas due to increasing contribution from the fermionic self-energy. We also show that the final state interaction increases with decreasing doping and gradually transforms the $2\Delta$ peak in the superconducting state into a pseudo resonance mode below $2\Delta$. We argue that these results agree well with the experimental data for Bi-2212.Comment: 6 pages, 4 eps figures. To appear in Solid State Com

Many-spinon states and the secret significance of Young tableaux

We establish a one-to-one correspondence between the Young tableaux classifying the total spin representations of N spins and the exact eigenstates of the the Haldane-Shastry model for a chain with N sites classified by the total spins and the fractionally spaced single-particle momenta of the spinons.Comment: 4 pages, 3 figure

Radial fall of a test particle onto an evaporating black hole

A test particle falling into a classical black hole crosses the event horizon and ends up in the singularity within finite eigentime. In the `more realistic' case of a `classical' evaporating black hole, an observer falling onto a black hole observes a sudden evaporation of the hole. This illustrates the fact that the discussion of the classical process commonly found in the literature may become obsolete when the black hole has a finite lifetime. The situation is basically the same for more complex cases, e.g. where a particle collides with two merging black holes. It should be pointed out that the model used in this paper is mainly of academic interest, since the description of the physics near a black hole horizon still presents a difficult problem which is not yet fully understood, but our model provides a valuable possibility for students to enter the interesting field of black hole physics and to perform numerical calculations of their own which are not very involved from the computational point of view.Comment: 6 pages, 3 figures, LATE

Capillary rise of water in hydrophilic nanopores

We report on the capillary rise of water in three-dimensional networks of hydrophilic silica pores with 3.5nm and 5nm mean radii, respectively (porous Vycor monoliths). We find classical square root of time Lucas-Washburn laws for the imbibition dynamics over the entire capillary rise times of up to 16h investigated. Provided we assume two preadsorbed strongly bound layers of water molecules resting at the silica walls, which corresponds to a negative velocity slip length of -0.5nm for water flow in silica nanopores, we can describe the filling process by a retained fluidity and capillarity of water in the pore center. This anticipated partitioning in two dynamic components reflects the structural-thermodynamic partitioning in strongly silica bound water layers and capillary condensed water in the pore center which is documented by sorption isotherm measurements.Comment: 4 pages, 3 figure

Unconventional properties of superconducting cuprates

We present an explanation of the unusual peak/dip/hump features observed in photoemission experiments on Bi2212 at $T \ll T_c$. We argue that these features arise from the interaction of the fermionic quasi-particles with overdamped spin fluctuations. We show that the strong spin-fermion interaction combined with the feedback effect on the spin damping due to superconductivity yields a Fermi-liquid form of the fermionic spectral function for $\omega < 2 \Delta$ where $\Delta$ is the maximum value of the superconducting gap, and a non-Fermi-liquid form for $\omega > 2 {\Delta}$. In the Fermi-liquid regime, the spectral function $A({\bf k}_F,\omega)$ displays a quasiparticle peak at $\omega = {\Delta}$; in the non-Fermi-liquid regime it possesses a broad maximum (hump) at $\omega \gg {\Delta}$. In between the two regimes, the spectral function has a dip at $\omega \sim 2 {\Delta}$. We argue that our theory also explains the tunneling data for the superconducting density of states.Comment: 4 pages, RevTeX, 4 eps figures embedded in the tex

Are there plasminos in superconductors?

Hot and/or dense, normal-conducting systems of relativistic fermions exhibit a particular collective excitation, the so-called plasmino. We compute the one-loop self-energy, the dispersion relation and the spectral density for fermions interacting via attractive boson exchange. It is shown that plasminos also exist in superconductors.Comment: 15 pages, 14 figures, revte