Tuning and Backreaction in F-term Axion Monodromy Inflation

We continue the development of axion monodromy inflation, focussing in particular on the backreaction of complex structure moduli. In our setting, the shift symmetry comes from a partial large complex structure limit of the underlying type IIB orientifold or F-theory fourfold. The coefficient of the inflaton term in the superpotential has to be tuned small to avoid conflict with Kahler moduli stabilisation. To allow such a tuning, this coefficient necessarily depends on further complex structure moduli. At large values of the inflaton field, these moduli are then in danger of backreacting too strongly. To avoid this, further tunings are necessary. In weakly coupled type IIB theory at the orientifold point, implementing these tunings appears to be difficult if not impossible. However, fourfolds or models with mobile D7-branes provide enough structural freedom. We calculate the resulting inflaton potential and study the feasibility of the overall tuning given the limited freedom of the flux landscape. Our preliminary investigations suggest that, even imposing all tuning conditions, the remaining choice of flux vacua can still be large enough for such models to provide a promising path to large-field inflation in string theory.Comment: 46 pages, 6 figures; v2: typos removed, references added; v3: references adde

Axions, Wormholes and Inflation in the String Landscape

This thesis explores the string theory landscape in two distinct approaches. First, we study dark radiation predictions in Large Volume Scenarios (LVS). Specifically, we realise the visible sector by D7-branes wrapping a 4-cycle. In consequence, the tension between the predicted effective number of relativistic species and recent cosmological measurements is reduced, and further ameliorated by accepting fine-tuning. Next, we investigate whether large-field inflation is consistent with quantum gravity. We propose realisations of axion monodromy inflation and alignment inflation in string theory. Due to backreaction of moduli on the inflaton, axion monodromy inflation requires potentially severe fine-tuning, which we realise on Calabi-Yau 4-folds, whereas we find no-go results on Calabi-Yau 3-folds. The severity of the tunings is quantified by the diminution of the landscape vacua after imposing the fine-tuning conditions. Furthermore, alignment inflation is realised by a winding trajectory in the field space of two complex structure moduli. Severe fine-tuning seems avoidable and consistency with the mild Weak Gravity Conjecture possible, albeit not with its strong version. Finally, we investigate the role of gravitational instantons for axion inflation. Although Giddings-Strominger wormholes are shown to induce corrections to the axion potential, a derivation of relevant constraints on the axion field range remains challenging

Bacterial and human peptidylarginine deiminases: targets for inhibiting the autoimmune response in rheumatoid arthritis?

Peptidylarginine deiminases (PADs) convert arginine within a peptide (peptidylarginine) into peptidylcitrulline. Citrullination by human PADs is important in normal physiology and inflammation. Porphyromonas gingivalis, a major pathogen in periodontitis, is the only prokaryote described to possess PAD. P. gingivalis infection may generate citrullinated peptides, which trigger anti-citrullinated peptide antibodies. In susceptible individuals, host protein citrullination by human PADs in the joint probably perpetuates antibody formation, paving the way for the development of chronic arthritis. Blockades of bacterial and human PADs may act as powerful novel therapies by inhibiting the generation of the antigens that trigger and sustain autoimmunity in rheumatoid arthritis

Heightened immune response to autocitrullinated porphyromonas gingivalis peptidylarginine deiminase: a potential mechanism for breaching immunologic tolerance in rheumatoid arthritis

Background: Rheumatoid arthritis (RA) is characterised by autoimmunity to citrullinated proteins, and there is increasing epidemiologic evidence linking Porphyromonas gingivalis to RA. P gingivalis is apparently unique among periodontal pathogens in possessing a citrullinating enzyme, peptidylarginine deiminase (PPAD) with the potential to generate antigens driving the autoimmune response. Objectives: To examine the immune response to PPAD in patients with RA, individuals with periodontitis (PD) and controls (without arthritis), confirm PPAD autocitrullination and identify the modified arginine residues. Methods: PPAD and an inactivated mutant (C351A) were cloned and expressed and autocitrullination of both examined by immunoblotting and mass spectrometry. ELISAs using PPAD, C351A and another P gingivalis protein arginine gingipain (RgpB) were developed and antibody reactivities examined in patients with RA (n=80), individuals with PD (n=44) and controls (n=82). Results: Recombinant PPAD was a potent citrullinating enzyme. Antibodies to PPAD, but not to Rgp, were elevated in the RA sera (median 122 U/ml) compared with controls (median 70 U/ml; p<0.05) and PD (median 60 U/ml; p<0.01). Specificity of the anti-peptidyl citrullinated PPAD response was confirmed by the reaction of RA sera with multiple epitopes tested with synthetic citrullinated peptides spanning the PPAD molecule. The elevated antibody response to PPAD was abolished in RA sera if the C351A mutant was used on ELISA. Conclusions: The peptidyl citrulline-specific immune response to PPAD supports the hypothesis that, as a bacterial protein, it might break tolerance in RA, and could be a target for therapy

Winding out of the Swamp: Evading the weak gravity conjecture with F-term winding inflation?

We present a new model of large field inflation along a winding trajectory in the field space of two axionic fields, where the “axions” originate from the complex structure moduli sector of a Calabi–Yau 3-fold at large complex structure. The winding trajectory arises from fixing one combination of axions by bulk fluxes and allows for a transplanckian effective field range. The inflaton potential arises from small “instantonic” corrections to the geometry and realises natural inflation. By working in a regime of large complex structure for two complex structure moduli the inflaton potential can be made subdominant without severe tuning. We also discuss the impact of the recent ‘no-go theorems’ for transplanckian axion periodicities on our work. Interestingly, our setup seems to realise a loophole pointed out in arXiv:1503.00795 and arXiv:1503.04783: our construction is a candidate for a string theory model of large field inflation which is consistent with the mild form of the weak gravity conjecture for axions

Alternative materials for high numerical aperture extreme ultraviolet lithography mask stacks

In this paper we compare the imaging performance of several options currently under consideration for use in 0.33 and higher numerical aperture (NA) extreme ultraviolet (EUV) mask stacks, Mo/Si ML reflective coatings with 40 bilayers, Ru/Si multilayer (ML) reflective coatings with 20 bilayers, and a new thinner Ni-based absorber layer on each of these mask stacks. The use of a Ru/Si ML coating with its shallower effective reflectance plane and a 2x thinner Ni-based absorber is expected to significantly reduce both shadow bias requirements and mask telecentricity errors. The conclusions of the paper are supported with the results of both experimental measurements and rigorous simulations.status: publishe