8,245 research outputs found
Quantum Mechanics Lecture Notes. Selected Chapters
These are extended lecture notes of the quantum mechanics course which I am
teaching in the Weizmann Institute of Science graduate physics program. They
cover the topics listed below. The first four chapter are posted here. Their
content is detailed on the next page. The other chapters are planned to be
added in the coming months.
1. Motion in External Electromagnetic Field. Gauge Fields in Quantum
Mechanics.
2. Quantum Mechanics of Electromagnetic Field
3. Photon-Matter Interactions
4. Quantization of the Schr\"odinger Field (The Second Quantization)
5. Open Systems. Density Matrix
6. Adiabatic Theory. The Berry Phase. The Born-Oppenheimer Approximation
7. Mean Field Approaches for Many Body Systems -- Fermions and Boson
Richness of dynamics and global bifurcations in systems with a homoclinic figure-eight
We consider 2D flows with a homoclinic figure-eight to a dissipative saddle. We study the rich dynamics that such a system exhibits under a periodic forcing. First, we derive the bifurcation diagram using topological techniques. In particular, there is a homoclinic zone in the parameter space with a non-smooth boundary. We provide a complete explanation of this phenomenon relating it to primary quadratic homoclinic tangency curves which end up at some cubic tangency (cusp) points. We also describe the possible attractors that exist (and may coexist) in the system. A main goal of this work is to show how the previous qualitative description can be complemented with quantitative global information. To this end, we introduce a return map model which can be seen as the simplest one which is 'universal' in some sense. We carry out several numerical experiments on the model, to check that all the objects predicted to exist by the theory are found in the model, and also to investigate new properties of the system
TOWARDS AN UNDERSTANDING OF EFFORTFUL FUNDRAISING EXPERIENCES: USING INTERPRETATIVE PHENOMENOLOGICAL ANALYSIS IN FUNDRAISING RESEARCH
Physical-activity oriented community fundraising has experienced an exponential growth in popularity over the past 15 years. The aim of this study was to explore the value of effortful fundraising experiences, from the point of view of participants, and explore the impact that these experiences have on people’s lives. This study used an IPA approach to interview 23 individuals, recognising the role of participants as proxy (nonprofessional) fundraisers for charitable organisations, and the unique organisation donor dynamic that this creates. It also bought together relevant psychological theory related to physical activity fundraising experiences (through a narrative literature review) and used primary interview data to substantiate these. Effortful fundraising experiences are examined in detail to understand their significance to participants, and how such experiences influence their connection with a charity or cause. This was done with an idiographic focus at first, before examining convergences and divergences across the sample. This study found that effortful fundraising experiences can have a profound positive impact upon community fundraisers in both the short and the long term. Additionally, it found that these experiences can be opportunities for charitable organisations to create lasting meaningful relationships with participants, and foster mutually beneficial lifetime relationships with them. Further research is needed to test specific psychological theory in this context, including self-esteem theory, self determination theory, and the martyrdom effect (among others)
THE DREAM OF A ZERO WASTE SOCIETY: EXPLORING THE PRACTICES AND BEHAVIOURS OF WASTE GENERATION IN GREATER MEXICO CITY
This research aims to re-conceptualise consumption and waste generation through a broader set of theoretical questions and analytical methodologies to establish a more holistic theoretical framework for comprehending the global South's "waste crisis." This thesis is primarily based on the following question: "why do we dispose of things?". By
focusing on practices and behaviours of consumption and disposal by citizens of GMC, this thesis seeks to unpack the networks, symbols, skills, and meanings of these practices.
This moves the conceptualisation of waste generation away from being conceived as an irremediable consequence of population growth or as primary responsibility on the
consumers' shoulders. Therefore, this thesis proposes that consumers are embedded in a "throwaway environment" that pushes them toward unsustainable practices. However, this does not mean that the consumers have a "throwaway culture"; consumers might be "carriers" of practices, but they are still active participants.
By unravelling the multiple layers of framing that aggregate into the consumption and disposal of citizens in GMC, we shall see how GMC society's historical, social, and political framework serves as dispositions that guide an individual to act. This study focuses on modifying the narrative of considering consumers as careless, lazy, or
consumption-driven. It also sheds light on how ignoring these behaviours and practices will only bring temporary and reactionary solutions when dealing with waste.
This dissertation also offers an analytical framework that explores how consumers' elements interrelate and are synergetic. By re-conceptualising consumption and waste
generation, I propose not focusing on the insidious moral narrative of whether consumption and disposal are acceptable and to what degree. Instead, we should concentrate on a policy strategy that will help reduce the flow of materials. As a result, we might be able to curve a waste crisis by accepting shared responsibility (mostly borne by governments and businesses
All I remember is forgetting
All I Remember is Forgetting is a novel about the complex weaving of memory, relationships and works of art. We observe these through the eyes of Roger Phillips, whom we first encounter washed up and living in his car after the failure of a third serious relationship. Unsuccessfully married twice, Roger has not navigated matrimony as well as he might. Instead he has escaped into a world of painting, photography and sculpture.
The main driving force behind the narrative is a wooden box containing Roger’s collection of 600 art postcards. These are pictures collected from galleries and museums around the world. Thirty years in the collecting, it took Roger’s second wife, Margot, only fifteen minutes to pitch them all into a landfill north of Auckland. Also missing were his most treasured books. Gone were all the stories from the myths of the Greeks and Romans on which he fed his imagination. So much so, in fact, that he is convinced that Eris, goddess of strife and discord, has been on a mission to ruin his life. While every book held special meaning, it was to each postcard that Roger attached his most personal recollections – the gallery, the surrounding city, the occasion and the person he was with. Each a complex narrative. All the memories of his life were tied to those small pieces of card; suddenly they were lost for ever. Art had always been Roger’s escape, his safe haven, but also his erotica, wrapping him in the beauty and hidden narratives in the lives of artists and their models. The imperfect fragments of Roger’s life show us that love is not best understood through art. Roger fails to see the philosophy of kintsugi, the Japanese art of golden repair. Breakage and mending are part of the history of your life, to be celebrated not disguised.
This is a many-layered exercise in ekphrasis, where dramatic verbal descriptions of works of art are layered with descriptions of Roger’s married life. In some cases both become so entwined that they form an entirely new layer of art. The novel weaves the highs and lows of Roger’s journey; both the pain and the humour. Through the lens of great art and its creators we find mirrors, reflections and the distortion between life and art. We travel from Sheffield and London to Paris and New York, before coming firmly to rest in New Zealand.
Do not believe everything that Roger tells you, but remember the words of Oscar Wilde: it is only through art that we can shield ourselves from the sordid perils of actual existence
Using Social Media to build a Counter-Power Movement: Multiple Sclerosis and CCSVI, a Case Study
The research is focused on a patient-based social media movement which advocated for clinical research into a discovery rejected by key elements of the medical establishment. This thesis aims to examine how social media interactions empowered patients, what motivated them to become a movement, and the elements which propelled the movement to create alternative patient associations.
This research comprises 62 individual, in-person, audio-recorded interviews with movement activists, and the researcher’s autoethnography as the founder and administrator of the movement’s Facebook Page. These methods are triangulated with academic publications, newspaper and television news, as well as other publicly-sourced materials relating to the case study.
The research finds that while the movement’s activities, from planning through protest, occurred solely on the streets of social media, activists experienced the same passion and urgency as the academic literature has described for on-the-street activists. That is, social media paralleled the “real streets” as a forum for the movement’s core activities. The research further finds that the traditional patient associations’ initial strategy of stonewalling the contested discovery was undercut by the momentum of the social media movement’s activities. They subsequently sought to quell the movement by lambasting social media as well as deploying a co-optation strategy, as described by the activists.
To conclude, social media function as streets and city halls where decisions taken can be implemented in the real world and permit geographically distributed as well as differently abled people to gather in significant numbers. The space where human interactions can foster social life and deepen personal emotional relations could be named the space of humanity. This is the space where timeless time and the realities of the counter power experience can happen, independent of whether that space is surrounded by real or digital bricks
Vacuum Energy in Modern Cosmology: an analysis of quantum field theory in curved spaces and its application to cosmological spacetimes
The last decades have witnessed an unprecedented advancement in our knowledge
of the large scale universe. In particular, increasingly accurate cosmological
observations have allowed us to discover a form of "dark energy", which
presently dominates the expansion of the universe. On the other hand,
fundamental problems in the standard cosmological model point towards the
possibility of a primordial inflationary period. Both these expansion phases
have in common the fact that they should be governed by forms of energy with
properties much similar to those of vacuum energy of classical or quantum
fields. In the meanwhile, quantum field theory in curved spaces (QFTCS) has
proved a rich framework to analyze phenomena of a quantum nature in regimes
where spacetime curvature is relevant, but not too extreme; particularly, it
yields novel insights on the structure and dynamics of quantum vacuum. In this
dissertation, we make a thorough exposition of the fundamentals of QFTCS and
present some of its applications in cosmological spacetimes. Particular
attention is given to the construction of an empirical notion of particles
through an idealized model of particle detectors, and to the phenomenon of
particle creation in expanding FLRW spacetimes. Further, we develop the
procedure of adiabatic renormalization, and use it to compute the renormalized
stress tensor in these spacetimes. For a noninteracting scalar field in de
Sitter spaces, we find that it takes the form of a cosmological constant,
although a quantitatively self-consistent value with the background expansion
can only be found at Planckian densities. We also present a construction of a
simple inflationary model, driven by a self-interacting classical scalar field,
and show how the quantized fluctuations of this field could give rise to a
nearly scale-invariant power spectrum, like the one that is currently observed
in the CMB.Comment: 246 page
A deep phenotyping approach to understand major depressive disorder and responses to antidepressant pharmacotherapy
Major depressive disorder (MDD) is a debilitating psychiatric disorder characterised by a complex underlying biology and poor response to pharmacological antidepressant strategies. Given the heterogeneity of MDD and the diverse range of available treatment options, there is an increasing desire to develop and implement precision medicine approaches to tailor existing treatment strategies to the biological system of the individual. In this thesis, high-resolution omics data (connectomics [fMRI], metabolomics [1H NMR] and immunomics [inflammatory cytokines]) collected from the Canadian Biomarker Integration Network in Depression (CAN-BIND) study has been integrated to facilitate the deep phenotyping of MDD. In addition, this approach has been used to predict the treatment response to two common antidepressant drugs, monotherapy with the selective serotonin reuptake inhibitor (SSRI) escitalopram (10-20 mg) or combination therapy with escitalopram and the dopaminergic antipsychotic aripiprazole (2-10 mg). This approach identified a multi-modal panel of sex-specific biomarkers of MDD and treatment response, highlighting a strong immunometabolic component in depressed males, but not females. Unsupervised clustering methods indicated the superiority of biological (neuroimaging) over symptom-based (clinical questionnaires) data for the stratification of patients into MDD subtypes with differential response to treatment. More importantly, a set of multi-modal, sex-specific biomarkers were identified that predicted treatment response with escitalopram monotherapy (84.7% accuracy) or aripiprazole augmentation (88.5% accuracy). In addition to highlighting potential new aspects of the biology of MDD (e.g. relevance of lipoprotein size and density for their relation to depression), this work is one of the first attempts to apply systems biology approaches to high-resolution biological data from a large clinical trial to predict later treatment outcome. With the validation of the findings presented in this thesis in independent cohorts, and with further development of omics technologies, leading to cheaper and high-throughput screening of the patient population, pre-dose biomarkers have the potential to achieve personalised treatment. Each year, escitalopram and aripiprazole are prescribed to an estimated 26 million and 7 million individuals respectively, and over one third of them do not respond. Thus, being able to predict response to antidepressant medication from baseline biomarkers has enormous clinical and socioeconomic benefits.Open Acces
Optimization Algorithms for Energy-Efficient Train Operations in Real-Time Rail Traffic Management
This thesis addresses the problem of achieving energy-efficient train operations in real-time rail traffic management. Due to traffic perturbations, dispatchers have to re-schedule train operations repeatedly to maintain circulation as smooth as possible, therefore minimizing the total delay. Along with re-scheduling decisions, train speed profiles have to be determined in such a way that a feasible train schedule is preserved and the total energy consumption is minimized.
First, we address a single-train real-time Energy-Efficient Train Control (EETC) problem, envisioned as a sub-problem of a hypothetical multiple-train Energy-Efficient Train Timetabling (EETT) problem for real-time traffic management applications. Precisely, we focus on determining an energy-optimal speed profile for a single train with a given schedule. We propose three algorithms: a constructive heuristic; a multi-start randomized constructive heuristic; and a Genetic Algorithm. We run experiments on real-life case studies provided by our industrial partner ALSTOM, which is a world leader in rail transport.
Second, we address a real-time multiple-train EETT problem known as the real-time Energy Consumption Minimization Problem (rtECMP), which is a subproblem of the real-time Rail Traffic Management Problem (rtRTMP). The rtECMP asks for deciding the speed profiles of multiple trains circulating in a given network during a given time window. The objective is to minimize the weighted sum of total delay and energy consumption. Rail infrastructures are represented with a microscopic level of detail including the interlocking system and signals.
We propose a graph-based rtECMP model and three meta-heuristic algorithms: Ant Colony Optimization (ACO); Iterated Local Search (ILS); and Greedy Randomized Adaptive Search Procedure (GRASP).
We run experiments on two real-life case studies, considering mixed dense traffic subject to perturbations
- …