Effective gravity and OSp(N,4) invariant matter

We re-examine the OSp(N,4) invariant interacting model of massless chiral and gauge superfields, whose superconformal invariance was instrumental, both in proving the all-order no-renormalization of the mass and chiral self-interaction lagrangians, and in determining the linear superfield renormalization needed. We show that the renormalization of the gravitational action modifies only the cosmological term, without affecting higher-order tensors. This could explain why the effect of the cosmological constant is shadowed by the effects of newtonian gravity.Comment: 12 pages, LaTeX, 4 figures, PACS: 04.65.+e, substantial revisions, to appear in Phys. Rev.

Influence of dimensionality on superconductivity in carbon nanotubes

We investigate the electronic instabilities in carbon nanotubes (CNs), looking for the break-down of the one dimensional Luttinger liquid regime due to the strong screening of the long-range part of the Coulomb repulsion. We show that such a breakdown is realized both in ultra-small single wall CNs and multi wall CNs, while a purely electronic mechanism could explain the superconductivity (SC) observed recently in ultra-small (diameter $\sim 0.4 nm$) single wall CNs ($T_c\sim 15 ^{o}K$) and entirely end-bonded multi-walled ones ($T_c\sim 12 ^{o}K$). We show that both the doping and the screening of long-range part of the electron-electron repulsion, needed to allow the SC phase, are related to the intrinsically 3D nature of the environment where the CNs operate.Comment: 5 pages, 3 figures, PACS: 71.10.Pm,74.50.+r,71.20.Tx, to appear in J. Phys. Cond. Ma

A modification of the 10d superparticle action inspired by the Gupta-Bleuler quantization scheme method

We reconsider the issue of the existence of a complex structure in the Gupta-Bleuler quantization scheme. We prove an existence theorem for the complex structure associated with the $d=10$ Casalbuoni-Brink-Schwarz superparticle, based on an explicitly constructed Lagrangian that allows a holomorphic-antiholomorphic splitting of the fermionic constraints consistent with the vanishing of all first class constraints on the physical states.Comment: 7 pages, LaTeX, to appear in Phys. Lett.

N=4 supersymmetric mechanics with nonlinear chiral supermultiplet

We construct N=4 supersymmetric mechanics using the N=4 nonlinear chiral supermultiplet. The two bosonic degrees of freedom of this supermultiplet parameterize the sphere S(2) and go into the bosonic components of the standard chiral multiplet when the radius of the sphere goes to infinity. We construct the most general action and demonstrate that the nonlinearity of the supermultiplet results in the deformation of the connection, which couples the fermionic degrees of freedom with the background, and of the bosonic potential. Also a non-zero magnetic field could appear in the system.Comment: 5 page

A new N = 8 nonlinear supermultiplet

We construct a new off-shell $\mathcal{N}{=}8$, $d{=}1$ nonlinear supermultiplet $(\mathbf{4,8,4})$ proceeding from the nonlinear realization of the $\mathcal{N}{=}8$, $d{=}1$ superconformal group $OSp(4^{\star}|4)$ in its supercoset $\frac{OSp(4^{\star}|4)}{SU(2)_{\mathcal{R}}\otimes \left\{D,K\right\} \otimes SO(4)}$. The irreducibility constraints for the superfields automatically follow from appropriate covariant conditions on the $osp(4^{\star}|4)$-valued Cartan superforms. We present the most general sigma-model type action for $(\mathbf{4,8,4})$ supermultiplet. The relations between linear and nonlinear $(\mathbf{4,8,4})$ supermultiplets and linear $\mathcal{N}{=}8$ $(\mathbf{5,8,3})$ vector supermultiplet are discussed.Comment: 15 pages, LaTeX file, PACS numbers: 11.30.Pb, 03.65.-

State-space Correlations and Stabilities

The state-space pair correlation functions and notion of stability of extremal and non-extremal black holes in string theory and M-theory are considered from the viewpoints of thermodynamic Ruppeiner geometry. From the perspective of intrinsic Riemannian geometry, the stability properties of these black branes are divulged from the positivity of principle minors of the space-state metric tensor. We have explicitly analyzed the state-space configurations for (i) the two and three charge extremal black holes, (ii) the four and six charge non-extremal black branes, which both arise from the string theory solutions. An extension is considered for the $D_6$-$D_4$-$D_2$-$D_0$ multi-centered black branes, fractional small black branes and two charge rotating fuzzy rings in the setup of Mathur's fuzzball configurations. The state-space pair correlations and nature of stabilities have been investigated for three charged bubbling black brane foams, and thereby the M-theory solutions are brought into the present consideration. In the case of extremal black brane configurations, we have pointed out that the ratio of diagonal space-state correlations varies as inverse square of the chosen parameters, while the off diagonal components vary as inverse of the chosen parameters. We discuss the significance of this observation for the non-extremal black brane configurations, and find similar conclusion that the state-space correlations extenuate as the chosen parameters are increased.Comment: 35 pages, Keywords: Black Hole Physics, Higher-dimensional Black Branes, State-space Correlations and Statistical Configurations. PACS numbers: 04.70.-s Physics of black holes; 04.70.Bw Classical black holes; 04.70.Dy Quantum aspects of black holes, evaporation, thermodynamics; 04.50.Gh Higher-dimensional black holes, black strings, and related object

On the Coulomb interaction in chiral-invariant one-dimensional electron systems

We consider a one-dimensional electron system, suitable for the description of the electronic correlations in a metallic carbon nanotube. Renormalization group methods are used to study the low-energy behavior of the unscreened Coulomb interaction between currents of well-defined chirality. In the limit of a very large number n of subbands we find a strong renormalization of the Fermi velocity, reminiscent of a similar phenomenon in the graphite sheet. For small n or sufficiently low energy, the Luttinger liquid behavior takes over, with a strong wavefunction renormalization leading to a vanishing quasiparticle weight. Our approach is appropriate to study the crossover from two-dimensional to one-dimensional behavior in carbon nanotubes of large radius.Comment: 8 pages, 2 figures, LaTeX, PACS: 71.27.+a, 73.20.D, 05.30.F