Inflation in models with Conformally Coupled Scalar fields: An application to the Noncommutative Spectral Action

Slow-roll inflation is studied in theories where the inflaton field is conformally coupled to the Ricci scalar. In particular, the case of Higgs field inflation in the context of the noncommutative spectral action is analyzed. It is shown that while the Higgs potential can lead to the slow-roll conditions being satisfied once the running of the self-coupling at two-loops is included, the constraints imposed from the CMB data make the predictions of such a scenario incompatible with the measured value of the top quark mass. We also analyze the role of an additional conformally coupled massless scalar field, which arises naturally in the context of noncommutative geometry, for inflationary scenarios.Comment: 14 pages, 3 figures Slightly modified version to match the one will appear in Phys.Rev.

A privileged quantum state from causal structure

This thesis investigates a new proposal for a privileged ground state of a free scalar quantum field in arbitrary regions of spacetime. This Sorkin-Johnston (SJ) state, implicit in work by S. Johnston on quantum field theory on causal sets, is defined solely in terms of the spacetime causal structure and is unique in any globally hyperbolic spacetime region. The first part of the thesis contains an analysis of the simplest possible setting: a flat two-dimensional causal interval. The simplicity of the setup makes analytic calculations tractable and allows for some general features of the state to be better understood. The second part deals with an investigation of the SJ state in de Sitter space. It turns out to be possible to construct the state explicitly using limiting procedures, which provides further interesting insights. In particular, the state is found to depend on the spacetime dimension, field mass, and on the choice of subregion, differing in many cases from the usual “Bunch-Davies” vacuum. The formalism does not select a unique state in spacetimes that are not globally hyperbolic, which include, among others, spacetimes exhibiting spatial topology change. These are relevant in the context of quantum gravity and in relation to the old question as to whether violent spacetime curvature fluctuations at Planckian scales can lead to changes in spatial topology, or whether such transitions are unphysical. Some efforts to understand the SJ state in the topology-changing two-dimensional “trousers” spacetime are discussed in the final part of the thesis.Open Acces

Boundary Terms for Causal Sets

We propose a family of boundary terms for the action of a causal set with a spacelike boundary. We show that in the continuum limit one recovers the Gibbons-Hawking-York boundary term in the mean. We also calculate the continuum limit of the mean causal set action for an Alexandrov interval in flat spacetime. We find that it is equal to the volume of the codimension-2 intersection of the two light-cone boundaries of the interval

alpha-nucleus potentials for the neutron-deficient p nuclei

alpha-nucleus potentials are one important ingredient for the understanding of the nucleosynthesis of heavy neutron-deficient p nuclei in the astrophysical gamma-process where these p nuclei are produced by a series of (gamma,n), (gamma,p), and (gamma,alpha) reactions. I present an improved alpha-nucleus potential at the astrophysically relevant sub-Coulomb energies which is derived from the analysis of alpha decay data and from a previously established systematic behavior of double-folding potentials.Comment: 6 pages, 3 figures, accepted for publication in Phys. Rev.

The show must go on: making money glamorizing oppression

This article presents an interdisciplinary analysis of the glamorization of the courtesan image as proposed by Baz Luhrmann’s film Moulin Rouge. The film sparked the appearance of high-street fashion inspired by the image of the 19th-century Parisian courtesan, which prompted the authors to examine how and why such images might appeal to female consumers. The critical analysis reaches beyond the images themselves to identify and discuss the modes of circulation of such images, and their function in achieving both the material ends of capitalism (ever-increasing consumption and production) and the promotion of one of the system’s core values (patriarchy). Moreover, the article hopes to illustrate the possibilities offered by integrating cultural and structural analyses of current social phenomena

α\alpha-particle condensate states in 16^{16}O

The existence of a rotational band with the $\alpha$+$^{12}$C($0_2^+$) cluster structure, in which three $\alpha$ particles in $^{12}$C($0_2^+$) are locally condensed, is demonstrated near the four-$\alpha$ threshold of $^{16}$O in agreement with experiment. This is achieved by studying structure and scattering for the $\alpha$+$^{12}$C($0_2^+$) system in a unified way. A drastic reduction (quenching) of the moment of the inertia of the $0^+$ state at 15.1 MeV just above the four-$\alpha$ threshold in $^{16}$O suggests that it could be a candidate for the superfluid state in $\alpha$-particle condensation.Comment: 5 pages, 3 figure

Nanoscale oxygen defect gradients in UO2+x surfaces.

Oxygen defects govern the behavior of a range of materials spanning catalysis, quantum computing, and nuclear energy. Understanding and controlling these defects is particularly important for the safe use, storage, and disposal of actinide oxides in the nuclear fuel cycle, since their oxidation state influences fuel lifetimes, stability, and the contamination of groundwater. However, poorly understood nanoscale fluctuations in these systems can lead to significant deviations from bulk oxidation behavior. Here we describe the use of aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy to resolve changes in the local oxygen defect environment in [Formula: see text] surfaces. We observe large image contrast and spectral changes that reflect the presence of sizable gradients in interstitial oxygen content at the nanoscale, which we quantify through first-principles calculations and image simulations. These findings reveal an unprecedented level of excess oxygen incorporated in a complex near-surface spatial distribution, offering additional insight into defect formation pathways and kinetics during [Formula: see text] surface oxidation

Nanoscale oxygen defect gradients in UO_2+x surfaces

Oxygen defects govern the behavior of a range of materials spanning catalysis, quantum computing, and nuclear energy. Understanding and controlling these defects is particularly important for the safe use, storage, and disposal of actinide oxides in the nuclear fuel cycle, since their oxidation state influences fuel lifetimes, stability, and the contamination of groundwater. However, poorly understood nanoscale fluctuations in these systems can lead to significant deviations from bulk oxidation behavior. Here we describe the use of aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy to resolve changes in the local oxygen defect environment in&nbsp;</p