Gravity from self-interaction redux

I correct some recent misunderstandings about, and amplify some details of, an old explicit non-geometrical derivation of GR.Comment: Final, amplified, published version; GRG (2009

Gauss-Bonnet Gravity with Scalar Field in Four Dimensions

We give all exact solutions of the Einstein-Gauss-Bonnet Field Equations coupled with a scalar field in four dimensions under certain assumptions.Comment: Latex file, 7 page

Exact solutions of Dirac equation on (1+1)-dimensional spacetime coupled to a static scalar field

We use a generalized scheme of supersymmetric quantum mechanics to obtain the energy spectrum and wave function for Dirac equation in (1+1)-dimensional spacetime coupled to a static scalar field.Comment: 7 pages, Late

Massive Gravity Simplified: A Quadratic Action

We present a simplified formulation of massive gravity where the Higgs fields have quadratic kinetic term. This new formulation allows us to prove in a very explicit way that all massive gravity theories considered so far inevitably have Boulware-Deser ghost in non-trivial fluctuations of background metric.Comment: 8 pages, paragraph added proving that Bianchi identity does not imply vanishing of linearized curvatur

Causal Structure of Vacuum Solutions to Conformal(Weyl) Gravity

Using Penrose diagrams the causal structure of the static spherically symmetric vacuum solution to conformal (Weyl) gravity is investigated. A striking aspect of the solution is an unexpected physical singularity at $r=0$ caused by a linear term in the metric. We explain how to calculate the deflection of light in coordinates where the metric is manifestly conformal to flat i.e. in coordinates where light moves in straight lines.Comment: 18 pages, 2 figures, title and abstract changed, contents essentially unaltered accepted for publication in General Relativity and Gravitatio

Racial and Ethnic Disparities in Dermatology Office Visits among Insured Patients, 2005-2010

Objective:To determine whether differences in race and ethnicity affect the usage of dermatological services. Methods: Data from the National Ambulatory Medical Care Survey were used to study trends in ethnic/race rates of outpatient dermatology office visits among publicly and privately insured patients from 2005-2010. In multivariable models, we explored the magnitude of ethnic/race differences in dermatology visit attendance for patients with public vs. private insurance. Results: From 2005-2010, dermatology visit utilization increased among insured Hispanics, but not among insured non-Hispanic Blacks or whites. Visits were less frequent by those with public insurance compared to private insurance. Privately and publicly insured visits were less common for non-Hispanic Blacks and Hispanics compared to whites after adjustment for patient demographics and primary visit diagnosis. Racial and ethnic differences in visit utilization rates were most apparent among non-referred visits. However, primary diagnoses for non-referred visits were similar across races and ethnicities, which suggests that differences in utilization may result from factors unrelated to clinical indications for care. Conclusion: Ethnic/race differences in the use of dermatological services in the United States may result from patient preferences for dermatologic care or health system related factors (e.g., insurance coverage regulations)

On the instability of classical dynamics in theories with higher derivatives

The development of instability in the dynamics of theories with higher derivatives is traced in detail in the framework of the Pais-Uhlenbeck fourth oder oscillator. For this aim the external friction force is introduced in the model and the relevant solutions to equations of motion are investigated. As a result, the physical implication of the energy unboundness from below in theories under consideration is revealed.Comment: 9 pages, no figures and no tables, revtex4; a few misprints are correcte