Conformal Truncation of Chern-Simons Theory at Large NfN_f

We set up and analyze the lightcone Hamiltonian for an abelian Chern-Simons field coupled to $N_f$ fermions in the limit of large $N_f$ using conformal truncation, i.e. with a truncated space of states corresponding to primary operators with dimension below a maximum cutoff $\Delta_{\rm max}$. In both the Chern-Simons theory, and in the $O(N)$ model at infinite $N$, we compute the current spectral functions analytically as a function of $\Delta_{\rm max}$ and reproduce previous results in the limit that the truncation $\Delta_{\rm max}$ is taken to $\infty$. Along the way, we determine how to preserve gauge invariance and how to choose an optimal discrete basis for the momenta of states in the truncation space.Comment: 32+25 pages, 8 figures. v2: updated ref

Thermalization, Viscosity and the Averaged Null Energy Condition

We explore the implications of the averaged null energy condition for thermal states of relativistic quantum field theories. A key property of such thermal states is the thermalization length. This lengthscale generalizes the notion of a mean free path beyond weak coupling, and allows finite size regions to independently thermalize. Using the eigenstate thermalization hypothesis, we show that thermal fluctuations in finite size `fireballs' can produce states that violate the averaged null energy condition if the thermalization length is too short or if the shear viscosity is too large. These bounds become very weak with a large number N of degrees of freedom but can constrain real-world systems, such as the quark-gluon plasma.Comment: 28 pages, 3 figure

Hydrodynamic theory of quantum fluctuating superconductivity

A hydrodynamic theory of transport in quantum mechanically phase-disordered superconductors is possible when supercurrent relaxation can be treated as a slow process. We obtain general results for the frequency-dependent conductivity of such a regime. With time-reversal invariance, the conductivity is characterized by a Drude-like peak, with width given by the supercurrent relaxation rate. Using the memory matrix formalism, we obtain a formula for this width (and hence also the dc resistivity) when the supercurrent is relaxed by short range Coulomb interactions. This leads to a new -- effective field theoretic and fully quantum -- derivation of a classic result on flux flow resistance. With strong breaking of time-reversal invariance, the optical conductivity exhibits what we call a `hydrodynamic supercyclotron' resonance. We obtain the frequency and decay rate of this resonance for the case of supercurrent relaxation due to an emergent Chern-Simons gauge field. The supercurrent decay rate in this `topologically ordered superfluid vortex liquid' is determined by the conductivities of the normal component of the liquid. Our work gives a controlled framework for low temperature metallic phases arising from phase-disordered superconductivity.Comment: 1 + 44 pages. 2 figures. v2 discussion improved in places. v3 sign errors fixed in section

Analysis of fibre tip damage risk during pulsed holmium laser application under water

Breaking of optical fibre tips during medical holmium laser applications involving endoscopic irradiation in a liquid environment, such as arthroscopy, has been reported. This represents a risk of complications due to foreign body reactions induced by quartz fragments remaining at the operation site. Fibre breakage has been analysed under controlled conditions at clinically used laser energies of 20-1000 mJ. The generation of pressure transients at the collapse of laser-induced vapour bubbles is identified as the mechanism of fibre tip destruction. Fibre damage is observed only in a confining liquid envivronment. The highest fibre damage occurrence is observed for laser fluences of 70-250 J cm-25 at the bare fibre tip, at pulse durations of 200-350 Μs. The fibre damage occurrence and extent increase with the fibre diameter. Avoiding the identified dangerous fluence range or use of fibres smaller than 400Μm diameter is recommended to perform endoscopic holmium laser application with minimal fibre damage ris