Dissecting holographic conductivities

The DC thermoelectric conductivities of holographic systems in which translational symmetry is broken can be efficiently computed in terms of the near-horizon data of the dual black hole. By calculating the frequency dependent conductivities to the first subleading order in the momentum relaxation rate, we give a physical explanation for these conductivities in the simplest such example, in the limit of slow momentum relaxation. Specifically, we decompose each conductivity into the sum of a coherent contribution due to momentum relaxation and an incoherent contribution, due to intrinsic current relaxation. This decomposition is different from those previously proposed, and is consistent with the known hydrodynamic properties in the translationally invariant limit. This is the first step towards constructing a consistent theory of charged hydrodynamics with slow momentum relaxation.Comment: v2: minor edits, matches published version. v1: 26 pages, 1 figur

Momentum dissipation and effective theories of coherent and incoherent transport

We study heat transport in two systems without momentum conservation: a hydrodynamic system, and a holographic system with spatially dependent, massless scalar fields. When momentum dissipates slowly, there is a well-defined, coherent collective excitation in the AC heat conductivity, and a crossover between sound-like and diffusive transport at small and large distance scales. When momentum dissipates quickly, there is no such excitation in the incoherent AC heat conductivity, and diffusion dominates at all distance scales. For a critical value of the momentum dissipation rate, we compute exact expressions for the Green's functions of our holographic system due to an emergent gravitational self-duality, similar to electric/magnetic duality, and SL(2,R) symmetries. We extend the coherent/incoherent classification to examples of charge transport in other holographic systems: probe brane theories and neutral theories with non-Maxwell actions.Comment: v1: 41 pages + appendices, 7 figures. v2: references and clarifications added. v3: reference adde

Incoherent transport in clean quantum critical metals

In a clean quantum critical metal, and in the absence of umklapp, most d.c. conductivities are formally infinite due to momentum conservation. However, there is a particular combination of the charge and heat currents which has a finite, universal conductivity. In this paper, we describe the physics of this conductivity $\sigma_Q$ in quantum critical metals obtained by charge doping a strongly interacting conformal field theory. We show that it satisfies an Einstein relation and controls the diffusivity of a conserved charge in the metal. We compute $\sigma_Q$ in a class of theories with holographic gravitational duals. Finally, we show how the temperature scaling of $\sigma_Q$ depends on certain critical exponents characterizing the quantum critical metal. The holographic results are found to be reproduced by the scaling analysis, with the charge density operator becoming marginal in the emergent low energy quantum critical theory.Comment: v1: 1 + 16 pages + reference

Privatization and Changes in the Wage Structure: Evidence from Firm Personnel Records

We investigate the wage effects of privatization using person-level firm-based panel datasets from one privatized and one nonprivatized public sector firm in the same country for the years immediately before and after privatization. Thus, we can analyze the before-after effects of privatization while controlling for individual and time fixed effects and allowing for firm-specific trends. Because the change in wage regime coincides with substantial losses in the market share of the privatized but not the nonprivatized firm, the situation approximates a natural experiment in switching workers from the public to the private sector. We find significant changes in the wage structure of the privatized but not the nonprivatized firm. Specifically, wage and wage growth distributions widened significantly after privatization. Conditioning on worker characteristics, we find that younger employees and those with shorter tenure gained from privatization, while high-skilled workers gained relative to medium-skilled workers. Surprisingly, low-skilled workers also gained, although seemingly in the form of temporary compensation intended to increase acceptance of privatization.privatization, liberalization, competition, labor markets, wage distributions

Methods and apparatus employing vibratory energy for wrenching Patent

Ultrasonic wrench for applying vibratory energy to mechanical fastener

Advanced action manipulator system (ADAMS)

Manipulator offers improved performance over other models in its category. It features larger force and reach capabilities and is readily convertible for underwater use. Unique kinematic arrangement provides extremely large working envelope. System has six degrees of motion: azimuth joint, shoulder joint, upper arm rotating joint, elbow joint, wrist pitch, and wrist twist

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

Torsional Newton-Cartan Geometry and Lifshitz Holography

We obtain the Lifshitz UV completion in a specific model for z=2 Lifshitz geometries. We use a vielbein formalism which enables identification of all the sources as leading components of well-chosen bulk fields. We show that the geometry induced from the bulk onto the boundary is a novel extension of Newton-Cartan geometry with a specific torsion tensor. We explicitly compute all the vevs including the boundary stress-energy tensor and their Ward identities. After using local symmetries/Ward identities the system exhibits 6+6 sources and vevs. The FG expansion exhibits, however, an additional free function which is related to an irrelevant operator whose source has been turned off. We show that this is related to a second UV completion.Comment: v2: 5 pages, matches version published in PR

Highly charged ions with E1, M1, and E2 transitions within laser range

Level crossings in the ground state of ions occur when the nuclear charge Z and ion charge Z_ion are varied along an isoelectronic sequence until the two outermost shells are nearly degenerate. We examine all available level crossings in the periodic table for both near neutral ions and highly charged ions (HCIs). Normal E1 transitions in HCIs are in X-ray range, however level crossings allow for optical electromagnetic transitions that could form the reference transition for high accuracy atomic clocks. Optical E1 (due to configuration mixing), M1 and E2 transitions are available in HCIs near level crossings. We present scaling laws for energies and amplitudes that allow us to make simple estimates of systematic effects of relevance to atomic clocks. HCI clocks could have some advantages over existing optical clocks because certain systematic effects are reduced, for example they can have much smaller thermal shifts. Other effects such as fine-structure and hyperfine splitting are much larger in HCIs, which can allow for richer spectra. HCIs are excellent candidates for probing variations in the fine-structure constant, alpha, in atomic systems as there are transitions with the highest sensitivity to alpha-variation

The Uncertain Foundation of Work Product

Work product is heavily litigated, extensively studied, and sorely misunderstood. Most blissfully accept it as a combination of codified rules and the seminal case of Hickman v. Taylor. This view settles for a superficial understanding that neither recognizes nor questions underlining assumptions. The codified rules are legislative mandates, Hickman is Supreme Court common law, and they define the doctrine differently. To understand its proper scope of work product, we must know the basis of Hickman v. Taylor, whether it can coexist with codified rules, and what happens when they conflict. This Article takes the novel view that work product is not one doctrine, but two. One branch consists of rules and statutes. The other branch is Hickman and its progeny. This Article concludes Hickman is the product of a well-recognized, if profoundly mysterious, strain in federal jurisprudence known as the inherent powers of courts. Even after the later adoption of codified work product rules, the Hickman branch survives but only in piecemeal fashion. When these branches conflict, the separation of powers requires that the rules and statutes preempt Hickman. To defend this claim, this Article takes us on a journey through the unexplored and striking origins of work product. From its unusual birth, to how courts struggled to make sense of it, to failed drafting attempts, an undercurrent emerges: there is an ongoing struggle between federal courts’ power to step in without any guidance to protect a policy of intrinsic importance to the justice system, and the need for deference to rules and statutes with a democratic pedigree. Ultimately, the near plenary power of the legislature to control federal courts resolves the conflict. This Article concludes Hickman is good law but is not absolute, Congress has more control over the attorney-client relationship than previously thought, and more material is discoverable than most attorneys or courts recognize