Mesoproterozoic Deposition, Regional Metamorphism and Deformation in North-Central New Mexico: Evidence from Metamorphic Monazite and Detrital Zircon Geochronology in the Picuris Mountains

Detrital zircon and metamorphic monazite ages from the Picuris Mountains, north central New Mexico, were used to confirm the depositional age of the Marquenas Formation, to document the depositional age of the Vadito Group, and to constrain the timing of metamorphism and deformation in the region. Detrital zircon 207Pb/206Pb ages were obtained with the LA-MC-ICPMS from quartzites collected from the type locality of the Marquenas Formation exposed at Cerro de las Marquenas, and from the lower Vadito Group in the southern and eastern Picuris Mountains. The Marquenas Formation sample yields 113 concordant ages including a Mesoproterozoic age population with four grains ca. 1470 Ga, a broad Paleoproterozoic age peak at 1695 Ma, and minor Archean age populations. Data confirm recent findings of Mesoproterozoic detrital zircons reported by Jones et al. (2011), and show that the Marquenas Formation is the youngest lithostratigraphic unit in the Picuris Mountains. Paleoproterozoic and Archean detrital grains in the Marquenas Formation are likely derived from local recycled Vadito Group rocks and ca. 1.75 Ga plutonic complexes, and ca. 1.46 detrital zircons were most likely derived from exposed Mesoproterozoic plutons south of the Picuris. Ninety-five concordant grains from each of two Vadito Group quartzites yield relatively identical unimodal Paleoproterozoic age distributions, with peaks at 1713-1707 Ma. Eastern exposures of quartzite mapped as Marquenas Formation yield detrital zircon age patterns and metamorphic mineral assemblages that are nearly identical to the Vadito Group. On this basis, I tentatively assigned the easternmost quartzite to the Vadito Group. Zircon grains in all samples show low U/Th ratios, welldeveloped concentric zoning, and no evidence of metamorphic overgrowth events, consistent with an igneous origin. North-directed paleocurrent indicators, such as tangential crossbeds (Soegaard & Eriksson, 1986) and other primary sedimentary structures, are preserved in the Marquenas Formation quartzite. Together with pebble-toboulder metaconglomerates in the Marquenas, these observations suggest that this formation was deposited in a braided alluvial plain environment in response to syntectonic uplift to the south of the Picuris Mountains. Metamorphic monazite from two Vadito Group quartzite samples were analyzed with an electron microprobe (EMP). Elemental compositional variation with respect to Th and Y define core and rim domains in monazite grains, and show lower concentrations of Th (1.46-1.52 wt%) and Y (0.67 wt%) in the cores, and higher concentrations of Th (1.98 wt%) and Y (1.06 wt%) in the rims. Results show that Mesoproterozoic core and rim ages from five grains overlap within uncertainty, ranging from 1395-1469 Ma with an average age of 1444 Ma. This 1.44 Ga average age is the dominant timing of metamorphic monazite growth in the region, and represents the timing of metamorphism experienced by the region. An older 1630 Ma core observed in sample CD10-12 may be interpreted as a result of low temperature metamorphism in lower Vadito Group rocks due to heat from ca. 1.65 Ga granitic intrusions. Core ages ca. 1.5 Ga are likely due to a mixing age of two different age domains during analyses. Confirmed sedimentation at 1.48-1.45 Ga and documented mid-crustal regional metamorphism in northern New Mexico ca. 1.44-1.40 are likely associated with a Mesoproterozoic orogenic event

THE EFFECTS OF DARK ENERGY AND BARYONS AND THEIR INTERPLAY ON THE GROWTH OF STRUCTURE

The discovery of the accelerated expansion of our Universe brought with it a new theoretical entity called dark energy. Within our standard model of cosmology, \lcdm{}, this dark energy component is described by a cosmological constant with a small energy density that does not evolve with space or time. Attempts to attribute physical meaning to the cosmological constant have been unsuccessful, culminating in a collection of problems known as the ``cosmological constant problem" and the ``coincidence problem". These have motivated alternative theories of dark energy that aim at relieving some of the theoretically unsatisfactory characteristics of the cosmological constant. Over recent years, observational cosmology has made great leaps in constraining the parameters of the standard model of cosmology. However, with the increasing quantity and quality of data available, a few tensions between different observational probes have started to appear. These have only grown over time and are now of statistical significance. These tensions could have any of the following origins; they arise from unknown and unaccounted systematic errors in the data, from unknown errors in the theoretical modeling and/or from an incomplete model of cosmology. The latter possibility has added motivation for extending the standard model of cosmology, where alternate forms of dark energy are one of many available avenues. The main aim of this work is to explore forms of dark energy with a greater degree of freedom than the cosmological constant. Specifically, dynamical dark energy (DDE) models which allow dark energy to evolve with time and are parametrised by two additional free parameters: $w_0$ and $w_a$. I investigate the current cosmological parameter constraints from a combination of observation data sets and devise a strategy to select 6 cosmologies of interest. I independently modified and ran a total of 12 simulations, evenly split between collissionless and hydrodynamic simulations. Since dark energy affects the expansion history, geometric probes, such as Type Ia supernovae and baryon acoustic oscillations, can constrain the dark energy parameters in a conceptually straightforward manner. However, changes to the expansion history also affect the growth of structure which could make large-scale structure (LSS) statistics potentially powerful and complementary probes. The first part of this work investigates the effect that these cosmologies have on a variety of LSS statistics using large cosmological hydrodynamical simulations. I find that DDE can affect the clustering of matter and haloes at the $\sim10\%$ level, which should be distinguishable with upcoming large-scale structure surveys. DDE cosmologies can also enhance or suppress the halo mass function (with respect to $\Lambda$CDM) over a wide range of halo masses. The internal properties of haloes are minimally affected by changes in DDE, however. The second part of this work investigates the separability of the cosmology and baryonic physics. I quantify to what extent these two processes affect each other, or in other words, how correlated they are. I show that the impact of baryons and associated feedback processes is largely independent of the change in cosmology and that these processes can be modelled separately to typically better than a few percent accuracy

Boundary quantum critical phenomena with entanglement renormalization

We extend the formalism of entanglement renormalization to the study of boundary critical phenomena. The multi-scale entanglement renormalization ansatz (MERA), in its scale invariant version, offers a very compact approximation to quantum critical ground states. Here we show that, by adding a boundary to the scale invariant MERA, an accurate approximation to the critical ground state of an infinite chain with a boundary is obtained, from which one can extract boundary scaling operators and their scaling dimensions. Our construction, valid for arbitrary critical systems, produces an effective chain with explicit separation of energy scales that relates to Wilson's RG formulation of the Kondo problem. We test the approach by studying the quantum critical Ising model with free and fixed boundary conditions.Comment: 8 pages, 12 figures, for a related work see arXiv:0912.289

Phase reconstruction of strong-field excited systems by transient-absorption spectroscopy

We study the evolution of a V-type three-level system, whose two resonances are coherently excited and coupled by two ultrashort laser pump and probe pulses, separated by a varying time delay. We relate the quantum dynamics of the excited multi-level system to the absorption spectrum of the transmitted probe pulse. In particular, by analyzing the quantum evolution of the system, we interpret how atomic phases are differently encoded in the time-delay-dependent spectral absorption profiles when the pump pulse either precedes or follows the probe pulse. We experimentally apply this scheme to atomic Rb, whose fine-structure-split 5s\,^2S_{1/2}\rightarrow 5p\,^2P_{1/2} and 5s\,^2S_{1/2}\rightarrow 5p\,^2P_{3/2} transitions are driven by the combined action of a pump pulse of variable intensity and a delayed probe pulse. The provided understanding of the relationship between quantum phases and absorption spectra represents an important step towards full time-dependent phase reconstruction (quantum holography) of bound-state wave-packets in strong-field light-matter interactions with atoms, molecules and solids.Comment: 5 pages, 4 figure