On the merit of a Central Limit Theorem-based approximation in statistical physics

The applicability conditions of a recently reported Central Limit Theorem-based approximation method in statistical physics are investigated and rigorously determined. The failure of this method at low and intermediate temperature is proved as well as its inadequacy to disclose quantum criticalities at fixed temperatures. Its high temperature predictions are in addition shown to coincide with those stemming from straightforward appropriate expansions up to (k_B T)^(-2). Our results are clearly illustrated by comparing the exact and approximate temperature dependence of the free energy of some exemplary physical systems.Comment: 12 pages, 1 figur

Adiabatic perturbation theory: from Landau-Zener problem to quenching through a quantum critical point

We discuss the application of the adiabatic perturbation theory to analyze the dynamics in various systems in the limit of slow parametric changes of the Hamiltonian. We first consider a two-level system and give an elementary derivation of the asymptotics of the transition probability when the tuning parameter slowly changes in the finite range. Then we apply this perturbation theory to many-particle systems with low energy spectrum characterized by quasiparticle excitations. Within this approach we derive the scaling of various quantities such as the density of generated defects, entropy and energy. We discuss the applications of this approach to a specific situation where the system crosses a quantum critical point. We also show the connection between adiabatic and sudden quenches near a quantum phase transitions and discuss the effects of quasiparticle statistics on slow and sudden quenches at finite temperatures.Comment: 20 pages, 3 figures, contribution to "Quantum Quenching, Annealing and Computation", Eds. A. Das, A. Chandra and B. K. Chakrabarti, Lect. Notes in Phys., Springer, Heidelberg (2009, to be published), reference correcte

Round table: Common sense in environmental impact assessment: it is not as common as it should be(with responses and a riposte)

Reviews of environmental impact assessment (EIA) practice, particularly by industrial proponents, have highlighted common shortfalls. EIA would benefit from more `common sense', which is not very common. For example, issue scoping usually includes too many inconsequential factors, and issues not directly affecting project decisions. Consideration of significance is often vague, misleading or inconsistent. Quality of environmental impact statements (EISs) leaves much to be desired, with EIS documents of little use to stakeholders. EIA guidance is a possible solution but is not always focused or applied sensibly. While we suggest more effective signals from government EIA regulators to project proponents to overcome these difficulties, our primary intention is to evoke discussion and provoke practitioners to take up the fight to improve the quality and integrity of EIAs