Hints of Universality from Inflection Point Inflation

This work aims to understand how cosmic inflation embeds into larger models of particle physics and string theory. Our work operates within a weakened version of the Landscape paradigm, wherein it is assumed that the set of possible Lagrangians is vast enough to admit the notion of a generic model. By focusing on slow-roll inflation, we examine the roles of both the scalar potential and the space of couplings which determine its precise form. In particular, we focus on the structural properties of the scalar potential, and find a surprising result: inflection point inflation emerges as an important —and under certain assumptions, dominant — possibility in the context of generic scalar potentials. We begin by a systematic coarse graining over the set of possible inflection point inflation models using V.I. Arnold’s ADE classification of singularities. Similar to du Val’s pioneering work on surface singularities, these determine structural classes for inflection point inflation which depened on a distinct number of control parameters. We consider both single and multifield inflation, and show how the various structural classes embed within each other. We also show how such control parameters influence the larger physical models in to which inflation is embedded. These techniques are then applied to both MSSM inflation and KKLT-type models of string cosmology. In the former case, we find that the scale of inflation can be entirely encoded within the super- potential of supersymmetric quantum field theories. We show how this relieves the fine-tuning required in such models by upwards of twelve orders of magnitude. Moreover, unnatural tuning between SUSY breaking and SUSY preserving sectors is eliminated without the explicit need for any hidden sector dynamics. In the later case, we discuss how structural stability vastly generalizes — and addresses — the Kallosh-Linde problem. Implications for the spectrum of SUSY breaking soft terms are then discussed, with an emphasis on how they may assist in constraining the inflationary scalar potential. We then pivot to a general discussion of the FLRW-scalar phase space, and show how inflection points induce caustics — or dynamical fixed points — amongst the space of possible trajectories. These fixed points are then used to argue that for uninformative priors on the space of couplings, the likelihood of inflection point inflation scales with the inverse cube of the number of e-foldings. We point out the geometric origin for the known ambiguity in the Liouville measure, and demonstrate of inflection point inflation ameliorates this problem. Finally we investigate the effect of the fixed point structure on the spectrum of density perturbations. We show how an anomaly in the Cosmic Mircowave Background data — low power at large scales — can be explained as a by product of the fixed point dynamics

What is the significance of oligocene melting in the Himalaya? - Oligocene melting and peak PT conditions: the moment of flow in the Himalaya?

Session - Large-Scale Deformatio

Controls on the 87Sr/86Sr ratio of carbonates in the Garhwal Himalaya, headwaters of the Ganges

The episodic variation of the seawater <SUP>87</SUP>Sr/<SUP>86</SUP>Sr ratio has been attributed to either variations in the Sr flux or the Sr-isotopic composition of the riverine-dissolved load derived from weathering of the continental crust. The discovery that Himalayan rivers are characterized by high concentrations of dissolved Sr concentrations with high 87Sr/86Sr ratios has raised the possibility that collisional orogens play a critical role in moderating the variations in seawater <SUP>87</SUP>Sr/<SUP>86</SUP>Sr ratios. Here we describe Himalayan carbonates and calc-silicates from Garhwal, the headwaters of the Ganges, with extreme <SUP>87</SUP>Sr/<SUP>86</SUP>Sr ratios (&gt;1.0). Elevated Sr-isotope ratios result from exchange with Rb-rich silicate material during both Himalayan and pre-Himalayan metamorphic episodes, and the carbonates contribute a significant fraction to the Ganges <SUP>87</SUP>Sr flux. Particularly elevated <SUP>87</SUP>Sr/<SUP>86</SUP>Sr ratios are found in calc-silicates from the Deoban Formation of the Lesser Himalaya. A detailed traverse of shales and calc-silicates from this unit confirms that carbonate horizons have increased <SUP>87</SUP>Sr/<SUP>86</SUP>Sr ratios as a result of isotopic exchange over length scales of 10-30 cm. We conclude that metamorphism of carbonates may cause elevation of their <SUP>87</SUP>Sr/<SUP>86</SUP>Sr ratios and that uplift of metamorphosed carbonates may be a consequence of collisional orogens, which contributes to the elevation of seawater <SUP>87</SUP>Sr/<SUP>86</SUP>Sr ratios

Burial and exhumation history of a Lesser Himalayan schist: Recording the formation of an inverted metamorphic sequence in NW India

Coupled analysis of the pressure–temperature (PT) evolution and accessory phase geochronology of a single sample reveals the burial-uplift history of part of the Lesser Himalaya during the Middle Miocene. Phase-equilibria calculations indicate that a peak temperature of 600–640 °C followed burial to approximately 25 km depth. Laser-ablation monazite geochronology yields a weighted mean 206Pb/238U age of 11.1 ± 2.0 Ma and a Tera-Wasserburg Concordia intercept age of 10.6 ± 0.9 Ma, with no distinguishable age difference between matrix and inclusion grains. Considerations of the likelihood of excess 206Pb further suggest that the crystallization age lies in the range 9–10 Ma. Textural analysis suggests that monazite grew during prograde metamorphism. Peak metamorphic conditions were followed by exhumation and cooling, forming a distinctively tight PT path closure. Both the shape of this path and its relatively young prograde phase distinguish Lesser Himalayan evolution from that typically inferred for the High Himalaya, and allow exploration of the thermal mechanisms that operated in the western Himalaya during the interval ca. 23–6 Ma. The PTt history is characteristic of footwall heating due to rapid overthrusting of hot rock (the Higher Himalaya), followed by incorporation into a thrust sheet that exhumed the sequence rapidly enough to preserve an inverted metamorphic gradient