Response of Bose gases in time-dependent optical superlattices

The dynamic response of ultracold Bose gases in one-dimensional optical lattices and superlattices is investigated based on exact numerical time evolutions in the framework of the Bose-Hubbard model. The system is excited by a temporal amplitude modulation of the lattice potential, as it was done in recent experiments. For regular lattice potentials, the dynamic signatures of the superfluid to Mott-insulator transition are studied and the position and the fine-structure of the resonances is explained by a linear response analysis. Using direct simulations and the perturbative analysis it is shown that in the presence of a two-colour superlattice the excitation spectrum changes significantly when going from the homogeneous Mott-insulator the quasi Bose-glass phase. A characteristic and experimentally accessible signature for the quasi Bose-glass is the appearance of low-lying resonances and a suppression of the dominant resonance of the Mott-insulator phase.Comment: 20 pages, 9 figures; added references and corrected typo

Where the rivers meet: the life story of the Reverend Helen Peters of Tanana

Thesis (M.A.) University of Alaska Fairbanks, 2014This thesis presents the life story of the Reverend Helen Peters, an Athabascan woman whose life exemplifies how faith in God can help a person to overcome great obstacles and trauma. The western view of leadership is very different from the concept as understood among Alaska Natives. Leadership of Native elders is the embodiment of their character, their conscience, their family history, traditions, language ability and spirituality. At every gathering the elders are expected to discuss these concepts in order to instruct and guide the people. In this way, they lead by example and find any and every opportunity to impart wisdom and knowledge. As an elder of Tanana, Helen understands the responsibility she has to lead the community. To this end, she wanted to tell her story, discussing difficult life experiences of substance abuse, domestic violence, sexual assault and suicide. These are the pressing subjects that she is most concerned about for her family and for the Native community at-large. Through personal experience, she understands that the silence surrounding her own story has kept her locked within herself and her family mired in the healing process, unable to move forward. She wanted to break that silence. In revealing these disturbing events, Helen courageously opens the door of dialogue that she hopes will lead not only to healing from past traumas but to confronting current situations in Native communities. She is attempting to lead the people to a place where it is permitted to talk about these difficult topics. This is her gift to her children and the community at-large. It is my goal to facilitate her intent and to offer Helen's story as an example of faithbased courage to overcome extreme obstacles. Helen's life also serves as a model of courage in taking a stand against alcohol and substance abuse, physical abuse and sexual abuse. May her candor inspire others to speak out so that the future is brighter for today's children.Chapter 1. Introduction, Helen Peters: A Woman of Faith -- 1.1. Why Her Story Matters -- 1.2. Methods -- 1.3. My Relationship with Helen and Our Process -- 1.4. Literature Review -- 1.5. Arrangement of the Thesis -- Chapter 2. Nuchalawoyya: A Brief History of Tanana -- 2.1. Bedzidehoodeno and the Battle of Morelock -- 2.2. The Americans -- 2.3. Church of England, Missionary Efforts -- Chapter 3. Growing up at the Mission -- 3.1. Grandmother Gaalno -- 3.2. Helen's Parents, Helen Luke and Elijah Joseph -- 3.3. Thoughts of Mother -- 3.4. The Memorial Potlatch -- 3.5. Anna Gertrude Sterne, Episcopal Deaconess -- 3.6. Life with Dad and Brothers -- 3.7. Old Ways and Fond Memories of Growing Up -- 3.8. School and English/Native Language -- 3.9. The Importance of Christmas as a Community -- 3.10. Caring for One Another -- 3.11. Outdoor Activities -- Chapter 4. Traditional Practices and Spiritual Matters -- 4.1. Medicine Men -- 4.2. Going Behind the Curtain -- 4.3. Nek'enle'eene -- 4.4. Reflections on Change -- Chapter 5. Life is Not So Rosy: Domestic Violence, Sexual Assault and Suicide -- 5.1. Sexual Assault -- 5.2. Abuse Cycle Continues -- 5.3. Visited by Suicide -- Chapter 6. Traditional Life Begins to Change -- 6.1. Death of Her Father -- 6.2. Mission Struggles and Closes -- 6.3. Gaalno Passes -- Chapter 7. Starting a Different Life: Moving to Fairbanks -- 7.1. Ladd Field -- 7.2. Don Andon- the Voice of KFAR -- 7.3. Rebuilding a Life -- 7.4. Hospital History -- 7.5. The One that Got Away: Coleman Inge -- 7.6. Getting Married -- 7.7. Raising Kids -- 7.8. Land Claims Meetings -- 7.9. Substance Abuse and Domestic Violence -- Chapter 8. Spiritual Journey and Renewal -- 8.1. Early Training in the Episcopal Church -- 8.2. Entering the Ministry -- 8.3. Heading to Arizona: Cook's School Training -- Chapter 9. Life Changes Forever -- 9.1. Marlene -- 9.2. Hardy Passes -- 9.3. Processing Grief -- 9.4. Memorial Potlatch for Marlene and Hardy in 1989 -- Chapter 10. Conclusion -- Bibliography -- Appendices

Recent Advances and Perspectives in Digital Image Correlation

International audienc

Review of the Laguerre-Gauss mode technology research program at Birmingham

Gravitational wave detectors from the advanced generation onwards are expected to be limited in sensitivity by thermal noise of the optics, making the reduction of this noise a key factor in the success of such detectors. A proposed method for reducing the impact of this noise is to use higher-order Laguerre-Gauss (LG) modes for the readout beam, as opposed to the currently used fundamental mode. We present here a synopsis of the research program undertaken by the University of Birmingham into the suitability of LG mode technology for future gravitational wave detectors. This will cover our previous and current work on this topic, from initial simulations and table-top LG mode experiments up to implementation in a prototype scale suspended cavity and high-power laser bench

Photon pressure induced test mass deformation in gravitational-wave detectors

A widely used assumption within the gravitational-wave community has so far been that a test mass acts like a rigid body for frequencies in the detection band, i.e. for frequencies far below the first internal resonance. In this article we demonstrate that localized forces, applied for example by a photon pressure actuator, can result in a non-negligible elastic deformation of the test masses. For a photon pressure actuator setup used in the gravitational wave detector GEO600 we measured that this effect modifies the standard response function by 10% at 1 kHz and about 100% at 2.5 kHz

Bose-Fermi mixtures in 1D optical superlattices

The zero temperature phase diagram of binary boson-fermion mixtures in two-colour superlattices is investigated. The eigenvalue problem associated with the Bose-Fermi-Hubbard Hamiltonian is solved using an exact numerical diagonalization technique, supplemented by an adaptive basis truncation scheme. The physically motivated basis truncation allows to access larger systems in a fully controlled and very flexible framework. Several experimentally relevant observables, such as the matter-wave interference pattern and the condensatefraction, are investigated in order to explore the rich phase diagram. At symmetric half filling a phase similar to the Mott-insulating phase in a commensurate purely bosonic system is identified and an analogy to recent experiments is pointed out. Furthermore a phase of complete localization of the bosonic species generated by the repulsive boson-fermion interaction is identified. These localized condensates are of a different nature than the genuine Bose-Einstein condensates in optical lattices.Comment: 18 pages, 9 figure

DC-readout of a signal-recycled gravitational wave detector

All first-generation large-scale gravitational wave detectors are operated at the dark fringe and use a heterodyne readout employing radio frequency (RF) modulation-demodulation techniques. However, the experience in the currently running interferometers reveals several problems connected with a heterodyne readout, of which phase noise of the RF modulation is the most serious one. A homodyne detection scheme (DC-readout), using the highly stabilized and filtered carrier light as local oscillator for the readout, is considered to be a favourable alternative. Recently a DC-readout scheme was implemented on the GEO 600 detector. We describe the results of first measurements and give a comparison of the performance achieved with homodyne and heterodyne readout. The implications of the combined use of DC-readout and signal-recycling are considered.Comment: 11 page

Triple Michelson Interferometer for a Third-Generation Gravitational Wave Detector

The upcoming European design study `Einstein gravitational-wave Telescope' represents the first step towards a substantial, international effort for the design of a third-generation interferometric gravitational wave detector. It is generally believed that third-generation instruments might not be installed into existing infrastructures but will provoke a new search for optimal detector sites. Consequently, the detector design could be subject to fewer constraints than the on-going design of the second generation instruments. In particular, it will be prudent to investigate alternatives to the traditional L-shaped Michelson interferometer. In this article, we review an old proposal to use three Michelson interferometers in a triangular configuration. We use this example of a triple Michelson interferometer to clarify the terminology and will put this idea into the context of more recent research on interferometer technologies. Furthermore the benefits of a triangular detector will be used to motivate this design as a good starting point for a more detailed research effort towards a third-generation gravitational wave detector.Comment: Minor corrections to the main text and two additional appendices. 14 pages, 6 figure

The upgrade of GEO600

The German / British gravitational wave detector GEO 600 is in the process of being upgraded. The upgrading process of GEO 600, called GEO-HF, will concentrate on the improvement of the sensitivity for high frequency signals and the demonstration of advanced technologies. In the years 2009 to 2011 the detector will undergo a series of upgrade steps, which are described in this paper.Comment: 9 pages, Amaldi 8 conference contributio

Spatial and temporal laser pulse shaping for two color excitation

Spatial and temporal laser pulse shaping is reported for two adjacent ranges of the laser spectrum. Thereto, two-photon excited fluorescence of dyes is measured for tailored pulses having two different spectral components which possess differently modulated spatial shapes. These particularly designed pulses are formed by using a 4f-temporal liquid crystal pulse shaper followed by a 2D-spatial shaper setup. Increased fluorescence contrasts between different dyes in a cuvette are recorded by selective phase shaping of the two adjacent spectral components. Moreover, two-photon excitation of the two spectral ranges from partially overlapping beams leads to spatially localized fluorescence in the overlap region. This is controlled by utilizing antisymmetric phase functions and can be applied to yield more complex two-photon excited fluorescence structures. The developed temporal and spatial shaping method of two-photon processes has valuable perspectives for optical and biophotonic applications