2,992 research outputs found

### 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

### 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

### Hyper-Kaehler geometry and dualization

We demonstrate that in N=8 supersymmetric mechanics with linear and nonlinear
chiral supermultiplets one may dualize two auxiliary fields into physical ones
in such a way that the bosonic manifold will be a hyper-Kaehler one. The key
point of our construction is about different dualizations of the two auxiliary
components. One of them is turned into a physical one in the standard way
through its replacement by the total time derivative of some physical field.
The other auxiliary field is dualized through a Lagrange multiplier. We clarify
this choice of dualization by presenting the analogy with a three-dimensional
case.Comment: 9 pages, LaTeX file, PACS numbers: 11.30.Pb, 03.65.-

### Superfield Formulation of Nonlinear N=4 Supermultiplets

We propose a unified superfield formulation of N=4 off-shell supermultiplets
in one spacetime dimension using the standard N=4 superspace. The main idea of
our approach is a "gluing" together of two linear supermultiplets along their
fermions. The functions defining such a gluing obey a system of equations. Each
solution of this system provides a new supermultiplet, linear or nonlinear,
modulo equivalence transformations. In such a way we reproduce all known linear
and nonlinear N=4, d=1 supermultiplets and propose some new ones. Particularly
interesting is an explicit construction of nonlinear N=4 hypermultiplets.Comment: 16 pages, no figure

### N=8 supersymmetric mechanics on the sphere S^3

Starting from quaternionic N=8 supersymmetric mechanics we perform a
reduction over a bosonic radial variable, ending up with a nonlinear off-shell
supermultiplet with three bosonic end eight fermionic physical degrees of
freedom. The geometry of the bosonic sector of the most general sigma-model
type action is described by an arbitrary function obeying the three dimensional
Laplace equation on the sphere S^3. Among the bosonic components of this new
supermultiplet there is a constant which gives rise to potential terms. After
dualization of this constant one may come back to the supermultiplet with four
physical bosons. However, this new supermultiplet is highly nonlinear. The
geometry of the corresponding sigma-model action is briefly discussed.Comment: 9 pages, LaTeX file, PACS: 11.30.Pb, 03.65.-

### Geometry of N=4, d=1 nonlinear supermultiplet

We construct the general action for $N=4, d=1$ nonlinear supermultiplet
including the most general interaction terms which depend on the arbitrary
function $h$ obeying the Laplace equation on $S^3$. We find the bosonic field
$B$ which depends on the components of nonlinear supermultiplet and transforms
as a full time derivative under N=4 supersymmetry. The most general interaction
is generated just by a Fayet-Iliopoulos term built from this auxiliary
component.
Being transformed through a full time derivative under $N=4, d=1$
supersymmetry, this auxiliary component $B$ may be dualized into a fourth
scalar field giving rise to a four dimensional $N=4, d=1$ sigma-model. We
analyzed the geometry in the bosonic sector and find that it is not a
hyper-K\"ahler one. With a particular choice of the target space metric $g$ the
geometry in the bosonic sector coincides with the one which appears in
heterotic $(4,0)$ sigma-model in $d=2$.Comment: 9 pages, LaTeX file, PACS: 11.30.Pb, 03.65.-

### The geometry of N=4 twisted string

We compare N=2 string and N=4 topological string within the framework of the
sigma model approach. Being classically equivalent on a flat background, the
theories are shown to lead to different geometries when put in a curved space.
In contrast to the well studied Kaehler geometry characterising the former
case, in the latter case a manifold has to admit a covariantly constant
holomorphic two-form in order to support an N=4 twisted supersymmetry. This
restricts the holonomy group to be a subgroup of SU(1,1) and leads to a
Ricci--flat manifold. We speculate that, the N=4 topological formalism is an
appropriate framework to smooth down ultraviolet divergences intrinsic to the
N=2 theory.Comment: 20 pages, LaTe

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