Galaxy Ecosystems: gas contents, inflows and outflows

We use a set of observational data for galaxy cold gas mass fraction and gas phase metallicity to constrain the content, inflow and outflow of gas in central galaxies hosted by halos with masses between $10^{11} M_{\odot}$ to $10^{12} M_{\odot}$. The gas contents in high redshift galaxies are obtained by combining the empirical star formation histories of Lu et al. (2014) and star formation models that relate star formation rate with the cold gas mass in galaxies. We find that the total baryon mass in low-mass galaxies is always much less than the universal baryon mass fraction since $z = 2$, regardless of star formation model adopted. The data for the evolution of the gas phase metallicity require net metal outflow at $z\lesssim 2$, and the metal loading factor is constrained to be about $0.01$, or about $60\%$ of the metal yield. Based on the assumption that galactic outflow is more enriched in metal than both the interstellar medium and the material ejected at earlier epochs, we are able to put stringent constraints on the upper limits for both the net accretion rate and the net mass outflow rate. The upper limits strongly suggest that the evolution of the gas phase metallicity and gas mass fraction for low-mass galaxies at $z < 2$ is not compatible with strong outflow. We speculate that the low star formation efficiency of low-mass galaxies is owing to some preventative processes that prevent gas from accreting into galaxies in the first place.Comment: 15 pages, 10 figures, submitted to MNRA

Quantum theory of the real and the complexified projective line

Quantum deformations of sets of points of the real and the complexified projective line are constructed. These deformations depend on the deformation parameter q and certain further parameters \lambda_{ij}. The deformations for which the subspace of polynomials of degree three has a basis of ordered monomials are selected. We show that the corresponding algebras of three points have "polynomiality". Invariant elements which turn out to be cross ratios in the classical limit are defined. For the special case |\lambda_{ij}| = 1 a quantum cross ratio with properties similar to the classical case is presented. As an application a quantum version of the real Euclidean distance is given.Comment: 25 page

A Note on N=2 Superstrings

In this note we investigate the generalised critical $N=2$ superstrings in $(1,2p)$ spacetime signature. We calculate the four-point functions for the tachyon operators of these theories. In contrast to the usual $N=2$ superstring in $(2,2)$ spacetime, the four-point functions do not vanish. The exchanged particles of the four-point function are included in the physical spectrum of the corresponding theory and have vanishing fermion charge.Comment: 8 pages, CTP TAMU-57/92, EFI-92-3

S^1-wrapped D3-branes on Conifolds

We construct a D3-brane wrapped on S^1, which is fibred over the resolved conifold as its transverse space. Whereas a fractional D3-brane on the resolved conifold is not supersymmetric and has a naked singularity, our solution is supersymmetric and regular everywhere. We also consider an $S^1$-wrapped D3-brane on the resolved cone over T^{1,1}/Z_2, as well as on the deformed conifold. In the former case, we obtain a regular supergravity dual to a certain four-dimensional field theory whose Lorentz and conformal symmetries are broken in the IR region and restored in the UV limit.Comment: Latex, 14 pages, minor correction

A Construction of Killing Spinors on S^n

We derive simple general expressions for the explicit Killing spinors on the n-sphere, for arbitrary n. Using these results we also construct the Killing spinors on various AdS x Sphere supergravity backgrounds, including AdS_5 x S^5$, AdS_4 x S^7 and AdS_7 x S^4. In addition, we extend previous results to obtain the Killing spinors on the hyperbolic spaces H^n.Comment: 11 pages, LaTe

Bayesian inferences of galaxy formation from the K-band luminosity and HI mass functions of galaxies: constraining star formation and feedback

We infer mechanisms of galaxy formation for a broad family of semi-analytic models (SAMs) constrained by the K-band luminosity function and HI mass function of local galaxies using tools of Bayesian analysis. Even with a broad search in parameter space the whole model family fails to match to constraining data. In the best fitting models, the star formation and feedback parameters in low-mass haloes are tightly constrained by the two data sets, and the analysis reveals several generic failures of models that similarly apply to other existing SAMs. First, based on the assumption that baryon accretion follows the dark matter accretion, large mass-loading factors are required for haloes with circular velocities lower than 200 km/s, and most of the wind mass must be expelled from the haloes. Second, assuming that the feedback is powered by Type-II supernovae with a Chabrier IMF, the outflow requires more than 25% of the available SN kinetic energy. Finally, the posterior predictive distributions for the star formation history are dramatically inconsistent with observations for masses similar to or smaller than the Milky-Way mass. The inferences suggest that the current model family is still missing some key physical processes that regulate the gas accretion and star formation in galaxies with masses below that of the Milky Way.Comment: 17 pages, 9 figures, 1 table, accepted for publication in MNRA