Dynamical local lattice instabilitiy triggered high tc superconductivity

High $T_c$ cuprate superconductors are characterized by two robust features: their strong electronic correlations and their intrinsic dynamical local lattice instabilities. Focusing on exclusively that latter, we picture their parent state in form of a quantum vacuum representing an electronic magma in which bound diamagnetic spin-singlet pairs pop in and out of existence in a Fermi sea of itinerant electrons. The mechanism behind that resides in the structural incompatibility of two stereo-chemical configurations Cu$^{\rm II}$O$_4$ and Cu$^{\rm III}$O$_4$ which compose the CuO$_2$ planes. It leads to spontaneously fluctuating Cu - O - Cu valence bonds which establish a local Feshbach resonance exchange coupling between bound and unbound electron pairs. The coupling, being the only free parameter in this scenario, the hole doping of the parent state is monitored by varying the total number of unpaired and paired electrons, in chemical equilibrium with each other. Upon lowering the temperature to below a certain $T^*$, bound and unbound electron pairs lock together in a local quantum superposition, generating transient localized bound electron pairs and a concomitant opening of a pseudo-gap in the single-particle density of states. At low temperature, this pseudo-gap state transits via a first order hole doping induced phase transition into a superconducting state in which the localized transient bound electron pairs get spatially phase correlated. The mechanism driving that transition is a phase separation between two phases having different relative densities of bound and unbound electron pairs, which is reminiscent of the physics of $^4$He - $^3$He mixtures.Comment: 9 pages 9 figure

Book Review: Missionaries, Rebellion and Proto-Nationalism: James Long of Bengal 1814-87

A review of Missionaries, Rebellion and Proto-Nationalism: James Long of Bengal 1814-87 by Geoffrey A. Oddie

On Hindutva and a Hindu-Catholic, with a Moral for our Times

The purpose of this article is to comment on the term hindutva, viz. Hinduness, with special reference to a 19th century Bengali thinker who sought to indigenise his Christian faith, and to draw some topical conclusions. The thinker is Brahmabandhab Upadhyay (1861-1907) whom his sometime friend, Rabindranath Tagore, Bengal\u27s greatest luminary, described as a Roman Catholic ascetic, yet a Vedantin -- spirited, fearless, self-denying, erudite and uncommonly influential. No doubt Upadhyay was influential then; he had a powerful impact on Tagore himself especially when they were jointly establishing what would later develop as Tagore\u27s brainchild of Santiniketan. For years previously Upadhyay had made a name for himself among the educated in the land in his attempt to give content to his self-description as a Hindu-Catholic, not only by a vigorous campaign of journalism and lectures but by his extraordinary life-style

Lucky joint action

In this paper, I argue that joint action permits a certain degree of luck. The cases I have in mind exhibit the following structure: each participant believes that the intended ends of each robustly support the joint action. This belief turns out to be false. Due to lucky circumstances, the discordance in intention never becomes common knowledge. However, common knowledge of the relevant intentions would have undermined the joint action altogether. The analysis of such cases shows the extent to which common knowledge of the participants’ intentions can be harmful to joint action. This extends a recent line of research that has questioned the necessity of common knowledge in joint action