Multi-black holes and instantons in effective string theory

The effective action for string theory which takes into account non-minimal coupling of moduli admits multi-black hole solutions. The euclidean continuation of these solutions can be interpreted as an instanton mediating the splitting and recombination of the throat of extremal magnetically charged black holes.Comment: 10 pages, plain Te

Quantum dilaton gravity as a linear dilaton conformal field theory

A model of matter-coupled gravity in two dimensions is quantized. The crucial requirement for performing the quantization is the vanishing of the conformal anomaly, which is achieved by tuning a parameter in the interaction potential. The spectrum of the theory is determined by mapping the model first onto a field theory with a Liouville interaction, then onto a linear dilaton conformal field theory. In absence of matter fields a pure gauge theory with massless ground state is found; otherwise it is possible to minimally couple up to 11 matter scalar fields: in this case the ground state is tachyonic and the matter sector decouples, like the transverse oscillators in the critical bosonic string.Comment: 7 pages, RevTeX4 file. v2: some comments and one reference adde

Sine-Gordon solitons, auxiliary fields, and singular limit of a double pendulums chain

We consider the continuum version of an elastic chain supporting topological and non-topological degrees of freedom; this generalizes a model for the dynamics of DNA recently proposed and investigated by ourselves. In a certain limit, the non-topological degrees of freedom are frozen, and the model reduces to the sine-Gordon equations and thus supports well-known topological soliton solutions. We consider a (singular) perturbative expansion around this limit and study in particular how the non-topological field assume the role of an auxiliary field. This provides a more general framework for the slaving of this degree of freedom on the topological one, already observed elsewhere in the context of the mentioned DNA model; in this framework one expects such phenomenon to arise in a quite large class of field-theoretical models.Comment: 18 pages, 2 figure

Dimensional reduction of 4d heterotic string black holes

We perform the spherical symmetric dimensional reduction $4d\to2d$ of heterotic string theory. We find a class of two-dimensional (2d) dilaton gravity models that gives a general description of the near-horizon, near-extremal behavior of four-dimensional (4d) heterotic string black holes. We show that the duality group of the 4d theory is realized in two dimensions in terms of Weyl transformations of the metric. We use the 2d dilaton gravity theory to compute the statistical entropy of the near-extremal 4d, $a=1/\sqrt3$, black hole.Comment: 12 pages, LaTex fil

Quantum gravitational corrections to black hole geometries

We calculate perturbative quantum gravity corrections to eternal two-dimensional black holes. We estimate the leading corrections to the AdS_2 black hole entropy and determine the quantum modification of N-dimensional Schwarzschild spacetime.Comment: 15 pages, 6 figures. Revised version: Introduction and conclusion expanded, section II reshaped, references added. Accepted for publication in Phys. Rev.

Facial nerve paralysis in acute otomastoiditis as presenting symptom of FAB M2, T8;21 leukemic relapse. Case report and review of the literature

Granulocytic sarcoma (chloroma) is a rare solid, extramedullary tumour composed of immature granulocytes, occurring during granulocytic leukemia. Leukemic involvement of the temporal bone is not uncommon and may present in a variety of ways. Symptomatic facial nerve paralysis is one of these. The authors report a case of facial nerve paralysis as the presenting symptom of leukemic relapse in a 16-year-old white male, affected by acute myelogenous leukemia FAB M2, karyotype 46xy, T8;21

Clinical associations of serum antiendothelial cell antibodies in patients with sudden sensorineural hearing loss

Objectives/Hypothesis: The role of antiendothelial cell antibodies in systemic vasculitis has been reported. The. aim of the study was to define the clinical associations of serum antiendothelial cell antibodies in patients with sudden sensorineural hearing loss. Study Design: A prospective study in patients with sudden sensorineural hearing loss. Methods: Serum samples were taken from 59 consecutive patients with sudden sensorineural hearing loss at time of presentation and from 28 normal control subjects. Indirect immunofluorescence assay was used to detect antiendothelial cell antibodies. Results: The prevalence of antiendothelial cell antibody detection was 54% (32 of 59 patients), with a statistically significant difference between patients and control subjects (P = .0064). Antiendothelial cell antibody positivity was significantly associated with absent recovery of hearing loss (P = .0020). Conclusions: The cytotoxicity to endothelial cells of the inner ear by antiendothelial cell antibody-positive sera might play a role in causing the stria vascularis damage in immune-mediated sudden sensorineural deafness. The appearance of antiendothelial cell antibody is related to the poor outcome of hearing loss, and its detection could be helpful in the selection of particular patients with sensorineural hearing loss for specific immunosuppressive treatments

Bertotti-Robinson type solutions to Dilaton-Axion Gravity

We present a new solution to dilaton-axion gravity which looks like a rotating Bertotti-Robinson (BR) Universe. It is supported by an homogeneous Maxwell field and a linear axion and can be obtained as a near-horizon limit of extremal rotating dilaton-axion black holes. It has the isometry $SL(2,R)\times U(1)$ where U(1) is the remnant of the SO(3) symmetry of BR broken by rotation, while $SL(2,R)$ corresponds to the $AdS_2$ sector which no longer factors out of the full spacetime. Alternatively our solution can be obtained from the D=5 vacuum counterpart to the dyonic BR with equal electric and magnetic field strengths. The derivation amounts to smearing it in D=6 and then reducing to D=4 with dualization of one Kaluza-Klein two-form in D=5 to produce an axion. Using a similar dualization procedure, the rotating BR solution is uplifted to D=11 supergravity. We show that it breaks all supersymmetries of N=4 supergravity in D=4, and that its higher dimensional embeddings are not supersymmetric either. But, hopefully it may provide a new arena for corformal mechanics and holography. Applying a complex coordinate transformation we also derive a BR solution endowed with a NUT parameter.Comment: 21 page

Propagation of twist solitons in real DNA chains

We report on numerical investigations concerning the propagation of solitons in a real DNA chain (the Human Adenovirus 2) using a realistic model of DNA torsional dynamics; this takes fully into account the inhomogeneities in the real chain. We find that twist solitons propagate for considerable distances (2-10 times their diameters) before stopping due to phonon emission. Our results show that twist solitons may exist in real DNA chains; and on a more general level that solitonic propagation can take place in highly inhomogeneous media.Comment: 6 pages, 3 figure