2,020 research outputs found
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
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
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