Quantum invariants of motion in a generic many-body system

Dynamical Lie-algebraic method for the construction of local quantum invariants of motion in non-integrable many-body systems is proposed and applied to a simple but generic toy model, namely an infinite kicked $t-V$ chain of spinless fermions. Transition from integrable via {pseudo-integrable (\em intermediate}) to quantum ergodic (quantum mixing) regime in parameter space is investigated. Dynamical phase transition between ergodic and intermediate (neither ergodic nor completely integrable) regime in thermodynamic limit is proposed. Existence or non-existence of local conservation laws corresponds to intermediate or ergodic regime, respectively. The computation of time-correlation functions of typical observables by means of local conservation laws is found fully consistent with direct calculations on finite systems.Comment: 4 pages in REVTeX with 5 eps figures include

Vision: a Lightweight Computing Model for Fine-Grained Cloud Computing

Cloud systems differ fundamentally in how they offer and charge for resources. While some systems provide a generic programming abstraction at coarse granularity, e.g., a virtual machine rented by the hour, others offer specialized abstractions with fine-grained accounting on a per-request basis. In this paper, we explore Tasklets, an abstraction for instances of short-duration, generic computations that migrate from a host requiring computation to hosts that are willing to provide computation. Tasklets enable fine-grained accounting of resource usage, enabling us to build infrastructure that supports trading computing resources according to various economic models. This computation model is especially attractive in settings where mobile devices can utilize resources in the cloud to mitigate local resource constraints

One-Loop Effective Action in Orbifold Compactifications

We employ the covariant background formalism to derive generic expressions for the one-loop effective action in field theoretic orbifold compactifications. The contribution of each orbifold sector is given by the effective action of its fixed torus with a shifted mass matrix. We thus study in detail the computation of the heat kernel on tori. Our formalism manifestly separates UV sensitive (local) from UV-insensitive (nonlocal) renormalization. To exemplify our methods, we study the effective potential of 6d gauge theory as well as kinetic terms for gravitational moduli in 11d supergravity.Comment: 30 pages, 1 figure, 3 tables, v2: appendix on zeta function regularization added, discussion of 6d example expanded, version to appear in JHE