Phenomenology of New Physics in the Neutrino Sector

This PhD thesis covers my work done at the KIT under the supervision of Prof. Thomas Schwetz-Mangold, in the field of neutrino-oscillation phenomenology. I first give an historical overview of neutrino physics, covering the Standard Model of particle physics, how the neutrino was discovered, and the experimental developments that led to the discovery of the neutrino, and subsequent experimental developments. Then I cover the latest analysis of the three-neutrino oscillation parameters with all relevant experimental data, which was done as a part of the NuFit collaboration. The global dataset contains opposing tendencies, which have low statistical significance, but may develop into a serious tension with future exposure. Then I cover my work undertaking a statistically rigorous analysis of the sterile-neutrino hypothesis, using data from terrestrial experiments, as well as solar data with a focus on the recent claimed evidence of sterile neutrinos from the Neutrino-4 and BEST experimental collaborations. The significant statistical tensions within the datasets are also evaluated, as the solar data constrains the sterile-neutrino hypothesis. Finally, I consider the so-called neutrino dipole portal, where a neutrino interacts with a new heavy neutral particle via a magnetic interaction. This interaction was proposed to explain an observed excess at MiniBooNE. I consider this type of interaction with the different flavours of neutrino at the future experiment DUNE, which will use new liquid-argon detector technology, which will be able to distinguish electron and photon tracks. I find that DUNE is well placed to probe the neutrino dipole portal at currently unconstrained parameter space, and will be competitive with other proposed experiments such as SHiP

Low temperature electroweak phase transition in the Standard Model with hidden scale invariance

We discuss a cosmological phase transition within the Standard Model which incorporates spontaneously broken scale invariance as a low-energy theory. In addition to the Standard Model fields, the minimal model involves a light dilaton, which acquires a large vacuum expectation value (VEV) through the mechanism of dimensional transmutation. Under the assumption of the cancellation of the vacuum energy, the dilaton develops a very small mass at 2-loop order. As a result, a flat direction is present in the classical dilaton-Higgs potential at zero temperature while the quantum potential admits two (almost) degenerate local minima with unbroken and broken eletroweak symmetry. We found that the cosmological electroweak phase transition in this model can only be triggered by a QCD chiral symmetry breaking phase transition at low temperatures, $T\lesssim 132$ MeV. Furthermore, unlike the standard case, the universe settles into the chiral symmetry breaking vacuum via a first-order phase transition which gives rise to a stochastic gravitational background with a peak frequency $\sim 10^{-8}$ Hz as well as triggers the production of approximately solar mass primordial black holes. The observation of these signatures of cosmological phase transitions together with the detection of a light dilaton would provide a strong hint of the fundamental role of scale invariance in particle physics

Bioactivities of Milk Polar Lipids in Influencing Intestinal Barrier Integrity, Systemic Inflammation, and Lipid Metabolism

The purpose of lactation is for nutrient provision and also importantly for protection from various environmental stressors. Milk polar lipids reduce cholesterol, protect against bacterial infection, reduce inflammation and help maintain gut integrity. Dynamic interactions within dietary fat, lipid metabolism, gut permeability and inflammatory cytokines remain unclear in the context of obesity and systemic inflammation. A rat model and three mouse models were developed to test the hypotheses that dietary milk polar lipids may affect lipid metabolism and intestinal integrity and may protect against systemic inflammation in the context of stressful diet, systemic inflammation, and obesity. The milk polar lipids isolates had complex effects on lipid metabolism and associated gene expression in the rat model. There were complex dynamics in lipid metabolism, gut permeability and systemic inflammation at different time points in all mouse models. The milk phospholipids increased gut permeability in genetic and diet-induced obesity and during the lipopolysaccharide (LPS) -induced inflammation. The phospholipids increased the plasma LPS level in genetic obesity and during the LPS stress. The phospholipids reduced liver mass and liver lipids in genetic obesity and during the LPS-induced inflammation. The phospholipids increased the body fat in the diet-induced obesity model. The milk gangliosides did not significantly affect gut permeability, systemic inflammation, and lipid metabolism in all three mouse models. Current estimate by the Centers for Disease Control is that about 1/3 Americans are obese (body mass index, BMI ≥ 30) and 1/3 Americans are overweight (25 ≤ BMI \u3c 30). More than 25% of Americans today have a fatty liver which could lead to further health problems. The data from this dissertation shed light on the complicated interrelationships between gut permeability, systemic inflammation, and lipid metabolism in obesity. The results contribute to our understanding of the bioactivities of milk polar lipids and provide scientific evidence for the role of milk polar lipids rich materials in affecting biological functions. The study of the influence of milk polar lipids on gut barrier integrity adds new information on understanding the mechanisms of gut leakiness and recovery. The investigation of the impact of milk polar lipids on lipid metabolism reveals new perspectives for the development of diet-induced obesity

Phase Changes in the Evolution of the IPv4 and IPv6 AS-Level Internet Topologies

In this paper we investigate the evolution of the IPv4 and IPv6 Internet topologies at the autonomous system (AS) level over a long period of time.We provide abundant empirical evidence that there is a phase transition in the growth trend of the two networks. For the IPv4 network, the phase change occurred in 2001. Before then the network's size grew exponentially, and thereafter it followed a linear growth. Changes are also observed around the same time for the maximum node degree, the average node degree and the average shortest path length. For the IPv6 network, the phase change occurred in late 2006. It is notable that the observed phase transitions in the two networks are different, for example the size of IPv6 network initially grew linearly and then shifted to an exponential growth. Our results show that following decades of rapid expansion up to the beginning of this century, the IPv4 network has now evolved into a mature, steady stage characterised by a relatively slow growth with a stable network structure; whereas the IPv6 network, after a slow startup process, has just taken off to a full speed growth. We also provide insight into the possible impact of IPv6-over-IPv4 tunneling deployment scheme on the evolution of the IPv6 network. The Internet topology generators so far are based on an inexplicit assumption that the evolution of Internet follows non-changing dynamic mechanisms. This assumption, however, is invalidated by our results.Our work reveals insights into the Internet evolution and provides inputs to future AS-Level Internet models.Comment: 12 pages, 21 figures; G. Zhang et al.,Phase changes in the evolution of the IPv4 and IPv6 AS-Level Internet topologies, Comput. Commun. (2010

Mixing navigation on networks

In this Letter, we proposed a mixing navigation mechanism, which interpolates between random-walk and shortest-path protocol. The navigation efficiency can be remarkably enhanced via a few routers. Some advanced strategies are also designed: For non-geographical scale-free networks, the targeted strategy with a tiny fraction of routers can guarantee an efficient navigation with low and stable delivery time almost independent of network size. For geographical localized networks, the clustering strategy can simultaneously increase the efficiency and reduce the communication cost. The present mixing navigation mechanism is of significance especially for information organization of wireless sensor networks and distributed autonomous robotic systems.Comment: 4 pages, and 7 figure

Electromechanically induced absorption in a circuit nano-electromechanical system

A detailed analysis of electromechanically induced absorption (EMIA) in a circuit nano-electromechanical hybrid system consisting of a superconducting microwave resonator coupled to a nanomechanical beam is presented. By performing two-tone spectroscopy experiments we have studied EMIA as a function of the drive power over a wide range of drive and probe tone detunings. We find good quantitative agreement between experiment and theoretical modeling based on the Hamiltonian formulation of a generic electromechanical system. We show that the absorption of microwave signals in an extremely narrow frequency band (\Delta\omega/2\pi <5 Hz) around the cavity resonance of about 6 GHz can be adjusted over a range of more than 25 dB on varying the drive tone power by a factor of two. Possible applications of this phenomenon include notch filters to cut out extremely narrow frequency bands (< Hz) of a much broader band of the order of MHz defined by the resonance width of the microwave cavity. The amount of absorption as well as the filtered frequency is tunable over the full width of the microwave resonance by adjusting the power and frequency of the drive field. At high drive power we observe parametric microwave amplification with the nanomechanical resonator. Due to the very low loss rate of the nanomechanical beam the drive power range for parametric amplification is narrow, since the beam rapidly starts to perform self-oscillations.Comment: 16 pages, 5 figure