Combining spectroscopic and photometric surveys using angular cross-correlations II: Parameter constraints from different physical effects

Future spectroscopic and photometric surveys will measure accurate positions and shapes of an increasing number of galaxies. In the previous paper of this series we studied the effects of Redshift Space Distortions (RSD), baryon acoustic oscillations (BAO) and Weak gravitational Lensing (WL) using angular cross-correlation. Here, we provide a new forecast that explores the contribution of including different observables, physical effects (galaxy bias, WL, RSD, BAO) and approximations (non-linearities, Limber approximation, covariance between probes). The radial information is included by using the cross-correlation of separate narrow redshift bins. For the auto correlation the separation of galaxy pairs is mostly transverse, while the cross-correlations also includes a radial component. We study how this information adds to our figure of merit (FoM), which includes the dark energy equation of state $w(z)$ and the growth history, parameterized by $\gamma$. We show that the Limber approximation and galaxy bias are the most critical ingredients to the modelling of correlations. Adding WL increases our FoM by 4.8, RSD by 2.1 and BAO by 1.3. We also explore how overlapping surveys perform under the different assumption and for different figures of merit. Our qualitative conclusions depend on the survey choices and scales included, but we find some clear tendencies that highlight the importance of combining different probes and can be used to guide and optimise survey strategies

Unimodular Trees versus Einstein Trees

The maximally helicity violating (MHV) tree level scattering amplitudes involving three, four or five gravitons are worked out in Unimodular Gravity. They are found to coincide with the corresponding amplitudes in General Relativity. This a remarkable result, insofar as both the propagators and the vertices are quite different in both theories.Comment: 20 pages, 5 figure

Modeling the angular correlation function and its full covariance in Photometric Galaxy Surveys

Near future cosmology will see the advent of wide area photometric galaxy surveys, like the Dark Energy Survey (DES), that extent to high redshifts (z ~ 1 - 2) but with poor radial distance resolution. In such cases splitting the data into redshift bins and using the angular correlation function $w(\theta)$, or the $C_{\ell}$ power spectrum, will become the standard approach to extract cosmological information or to study the nature of dark energy through the Baryon Acoustic Oscillations (BAO) probe. In this work we present a detailed model for $w(\theta)$ at large scales as a function of redshift and bin width, including all relevant effects, namely nonlinear gravitational clustering, bias, redshift space distortions and photo-z uncertainties. We also present a model for the full covariance matrix characterizing the angular correlation measurements, that takes into account the same effects as for $w(\theta)$ and also the possibility of a shot-noise component and partial sky coverage. Provided with a large volume N-body simulation from the MICE collaboration we built several ensembles of mock redshift bins with a sky coverage and depth typical of forthcoming photometric surveys. The model for the angular correlation and the one for the covariance matrix agree remarkably well with the mock measurements in all configurations. The prospects for a full shape analysis of $w(\theta)$ at BAO scales in forthcoming photometric surveys such as DES are thus very encouraging.Comment: 23 pages, 21 figures Revised version accepted by MNRAS. Description of mocks re-structured. Mocks including redshift distortions and Photo-z publicly available at http://www.ice.cat/mic

Cosmological constraints from multiple tracers in spectroscopic surveys

We use the Fisher matrix formalism to study the expansion and growth history of the Universe using galaxy clustering with 2D angular cross-correlation tomography in spectroscopic or high resolution photometric redshift surveys. The radial information is contained in the cross correlations between narrow redshift bins. We show how multiple tracers with redshift space distortions cancel sample variance and arbitrarily improve the constraints on the dark energy equation of state $\omega(z)$ and the growth parameter $\gamma$ in the noiseless limit. The improvement for multiple tracers quickly increases with the bias difference between the tracers, up to a factor $\sim4$ in $\text{FoM}_{\gamma\omega}$. We model a magnitude limited survey with realistic density and bias using a conditional luminosity function, finding a factor 1.3-9.0 improvement in $\text{FoM}_{\gamma\omega}$ -- depending on global density -- with a split in a halo mass proxy. Partly overlapping redshift bins improve the constraints in multiple tracer surveys a factor $\sim1.3$ in $\text{FoM}_{\gamma\omega}$. This findings also apply to photometric surveys, where the effect of using multiple tracers is magnified. We also show large improvement on the FoM with increasing density, which could be used as a trade-off to compensate some possible loss with radial resolution.Comment: 20 pages, 15 figure

The Business Cycles of Balance-of-Payment Crises: A Revision of Mundellan Framework

In his seminal 1960 article Robert Mundell proposed a model of balance-of-payments crises in which confidence in the continuation of a currency peg depended on the observed holdings of central bank foreign reserves. We examine the implications of a reformulation of this view from the perspective of an equilibrium business cycle model in which the probability of devaluation is an endogenous variable conditioned on foreign reserves. The model explains some business cycle regularities of exchange-rate-based stabilizations while also producing devaluation probabilities that capture some features of devaluation probabilities estimated in the data. The analysis aims to explain both the real effects and the collapse of temporary fixed-exchange-rate regimes in an unified framework, and provides an economic interpretation for the evidence that foreign reserves are a robust leading indicator of currency crises.

Devaluation Risk and the Syndrome of Exchange-Rate-Based Stabilizations

This paper shows that the risk of devaluation can be an important factor accounting for the stylized facts of exchange-rate-based stabilizations. This conclusion follows from studying the quantitative implications of a two-sector equilibrium business cycle model of a small open economy calibrated to Mexico's 1987-1994 stabilization plan. In the model a time-variant interest rate differential that acts as a stochastic tax on money demand, labor supply, investment, and saving. Under incomplete markets, this tax induces endogenous state-contingent wealth effects via fiscal adjustment and suboptimal investment. Devaluation risk entails large welfare costs in this environment.

Interactions between Eriosyce villicumensis (Cactaceae) and shrubs: a study case in the hyper arid Monte desert of Argentina

Se estudió la distribución espacial intraespecífica e interespecífica de Eriosyce villicumensis (Rausch) Katt. en tres unidades fisiográficas y a microescala bajo los arbustos. Se analizó la influencia de los arbustos en la radiación fotosintéticamente activa y temperatura del suelo. La distribución intraespecífica de E. villicumensis resultó aleatoria. La distribución interespecífica estuvo asociada con Larrea cuneifolia y/o Zuccagnia punctata, observándose disminución de asociación desde el centro al borde de los arbustos, coincidiendo con los gradientes de luz y temperatura detectados bajo los arbustos. En ambientes desérticos, la interacción entre especies es una estrategia que permite la supervivencia de varias especies.The spatial intraspecific and interspecific distribution of Eriosyce villicumensis (Rausch) Katt. was studied in three physiographic units and at micro-scale under shrubs. The influence of shrubs on photosynthetically active radiation and on soil temperature was analyzed. The intraspecific distribution of E. villicumensis was random. The interspecific distribution was highly associated with Larrea cuneifolia and/or Zuccagnia punctata, observing decreasing association from the centre toward the edge of shrub canopies, coinciding with both the light and temperature gradients detected under those shrubs. In desert environments, the interaction between species is a strategy that allows survival of several plants.Fil: Almiron, Martin Guillermo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Martinez Carretero, Eduardo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentin