BVR photometry of the resolved dwarf galaxy Ho IX

We present BVR CCD photometry down to limiting magnitude B=23.5 mag for 232 starlike objects and 11 diffuse objects in a 5.4' x 5.4' field of Ho IX. The galaxy is a gas-rich irregular dwarf galaxy possibly very close to M 81, which makes it especially interesting in the context of the evolution of satellite galaxies and the accretion of dwarf galaxies. Investigations of Ho IX were hampered by relatively large contradictions in the magnitude scale between earlier studies. With our new photometry we resolved these discrepancies. The color magnitude diagram (CMD) of Ho IX is fairly typical of a star-forming dwarf irregular, consistent with earlier results. Distance estimates from our new CMD are consistent with Ho IX being very close to M 81 and therefore being a definite member of the M 81 group, apparently in very close physical proximity to M 81.Comment: 9 pages, 8 figures, uses aa.cls, A&A in pres

Tropospheric HO2 determination by FAGE

The detection efficiency is greatest at low pressures, where the subsequent removal of the HO product by the NO reagent (via HO + NO + M yields HONO + M) is relatively slow. Moreover, nozzle expansion of the air from ambient to low pressures produces a turbulent zone that assists in mixing the reagent with the sample. If the HO product is observed by laser-excited fluorescence, then the other advantages of low-pressure detection by FAGE (Fluorescence Assay with Gas Expansion) also apply. The FAGE instrumental response was calibrated to external HO2 by observing NO decay in the photolysis of HO-CH2O mixtures and by choosing conditions in which HO2 + NO is the only significant NO destruction path. HO2 was determined in urban air

Local suppression of the hidden order phase by impurities in URu2Si2

We consider the effects of impurities on the enigmatic hidden order (HO) state of the heavy-fermion material URu2Si2. In particular, we focus on local effects of Rh impurities as a tool to probe the suppression of the HO state. To study local properties we introduce a lattice free energy, where the time invariant HO order parameter "psi" and local antiferromagnetic (AFM) order parameter M are competing orders. Near each Rh atom the HO order parameter is suppressed, creating a hole in which local AFM order emerges as a result of competition. These local holes are created in the fabric of the HO state like in a Swiss cheese and "filled" with droplets of AFM order. We compare our analysis with recent NMR results on URu2Si2 doped with Rh and find good agreement with the data.Comment: 8 pages, 6 figure

Perfect fluid tori orbiting Kehagias-Sfetsos naked singularities

We construct perfect fluid tori in the field of the Kehagias-Sfetsos (K-S) naked singularity representing spherically symmetric vacuum solution of the modified Ho\v{r}ava quantum gravity that is characterized by a dimensionless parameter $\omega M^2$, combining the gravitational mass parameter $M$ of the spacetime with the Ho\v{r}ava parameter $\omega$ reflecting the role of the quantum corrections. In dependence on the value of $\omega M^2$, the K-S naked singularities demonstrate a variety of qualitatively different behavior of their circular geodesics that is fully reflected in the properties of the toroidal structures. In all of the K-S naked singularity spacetimes the tori are located above an "antigravity" sphere where matter can stay in stable equilibrium position, that is relevant for the stability of the orbiting fluid toroidal accretion structures.Comment: 44 pages, 27 figures multi panel

Heterotic and type I strings from twisted supermembranes

As shown by Ho\v{r}ava and Witten, there are gravitational anomalies at the boundaries of $M^{10}\times S^1/Z_2$ of 11 dimensional supergravity. They showed that only 10 dimensional vector multiplets belonging to $E_8$ gauge group can be consistently coupled to this theory. Thus, the dimensional reduction of this theory should be the low energy limit of the $E_8\times E_8$ heterotic string. Here we assume that M-theory is a theory of supermembranes which includes twisted supermembranes. We show that for a target space $M^{10}\times S^1/Z_2$, in the limit in which $S^1/Z_2$ is small, the effective action is the $E_8\times E_8$ heterotic string. We also consider supermembranes on $M^{9}\times S^1\times S^1/Z_2$ and find the dualities expected from 11 dimensional supergravity on this manifold. We show that the requirements for worldsheet anomaly cancellations at the boundaries of the worldvolume action are the same requirements imposed on the Ho\v{r}ava-Witten action.Comment: 17 pages, Late