1,051 research outputs found
Sliding coherence window technique for hierarchical detection of continuous gravitational waves
A novel hierarchical search technique is presented for all-sky surveys for
continuous gravitational-wave sources, such as rapidly spinning nonaxisymmetric
neutron stars. Analyzing yearlong detector data sets over realistic ranges of
parameter space using fully coherent matched-filtering is computationally
prohibitive. Thus more efficient, so-called hierarchical techniques are
essential. Traditionally, the standard hierarchical approach consists of
dividing the data into nonoverlapping segments of which each is coherently
analyzed and subsequently the matched-filter outputs from all segments are
combined incoherently. The present work proposes to break the data into
subsegments shorter than the desired maximum coherence time span (size of the
coherence window). Then matched-filter outputs from the different subsegments
are efficiently combined by sliding the coherence window in time: Subsegments
whose timestamps are closer than coherence window size are combined coherently,
otherwise incoherently. Compared to the standard scheme at the same coherence
time baseline, data sets longer by about 50-100% would have to be analyzed to
achieve the same search sensitivity as with the sliding coherence window
approach. Numerical simulations attest to the analytically estimated
improvement.Comment: 11 pages, 4 figure
Parameter-space correlations of the optimal statistic for continuous gravitational-wave detection
The phase parameters of matched-filtering searches for continuous
gravitational-wave signals are sky position, frequency and frequency
time-derivatives. The space of these parameters features strong global
correlations in the optimal detection statistic. For observation times smaller
than one year, the orbital motion of the Earth leads to a family of
global-correlation equations which describes the "global maximum structure" of
the detection statistic. The solution to each of these equations is a different
hypersurface in parameter space. The expected detection statistic is maximal at
the intersection of these hypersurfaces. The global maximum structure of the
detection statistic from stationary instrumental-noise artifacts is also
described by the global-correlation equations. This permits the construction of
a veto method which excludes false candidate events.Comment: 17 pages, 10 figure
Efficient generation and optimization of stochastic template banks by a neighboring cell algorithm
Placing signal templates (grid points) as efficiently as possible to cover a
multi-dimensional parameter space is crucial in computing-intensive
matched-filtering searches for gravitational waves, but also in similar
searches in other fields of astronomy. To generate efficient coverings of
arbitrary parameter spaces, stochastic template banks have been advocated,
where templates are placed at random while rejecting those too close to others.
However, in this simple scheme, for each new random point its distance to every
template in the existing bank is computed. This rapidly increasing number of
distance computations can render the acceptance of new templates
computationally prohibitive, particularly for wide parameter spaces or in large
dimensions. This work presents a neighboring cell algorithm that can
dramatically improve the efficiency of constructing a stochastic template bank.
By dividing the parameter space into sub-volumes (cells), for an arbitrary
point an efficient hashing technique is exploited to obtain the index of its
enclosing cell along with the parameters of its neighboring templates. Hence
only distances to these neighboring templates in the bank are computed,
massively lowering the overall computing cost, as demonstrated in simple
examples. Furthermore, we propose a novel method based on this technique to
increase the fraction of covered parameter space solely by directed template
shifts, without adding any templates. As is demonstrated in examples, this
method can be highly effective..Comment: PRD accepte
Gamma-ray Timing of Redback PSR J2339-0533: Hints for Gravitational Quadrupole Moment Changes
We present the results of precision gamma-ray timing measurements of the
binary millisecond pulsar PSR J23390533, an irradiating system of "redback"
type, using data from the Fermi Large Area Telescope. We describe an optimized
analysis method to determine a long-term phase-coherent timing solution
spanning more than six years, including a measured eccentricity of the binary
orbit and constraints on the proper motion of the system. A major result of
this timing analysis is the discovery of an extreme variation of the nominal
4.6-hour orbital period over time, showing alternating epochs of
decrease and increase. We inferred a cyclic modulation of with an
approximate cycle duration of 4.2 years and a modulation amplitude of . Considering different possible
physical causes, the observed orbital-period modulation most likely results
from a variable gravitational quadrupole moment of the companion star due to
cyclic magnetic activity in its convective zone.Comment: 9 pages, 2 figure
Optimized Blind Gamma-ray Pulsar Searches at Fixed Computing Budget
The sensitivity of blind gamma-ray pulsar searches in multiple years worth of
photon data, as from the Fermi LAT, is primarily limited by the finite
computational resources available. Addressing this "needle in a haystack"
problem, we here present methods for optimizing blind searches to achieve the
highest sensitivity at fixed computing cost. For both coherent and semicoherent
methods, we consider their statistical properties and study their search
sensitivity under computational constraints. The results validate a multistage
strategy, where the first stage scans the entire parameter space using an
efficient semicoherent method and promising candidates are then refined through
a fully coherent analysis. We also find that for the first stage of a blind
search incoherent harmonic summing of powers is not worthwhile at fixed
computing cost for typical gamma-ray pulsars. Further enhancing sensitivity, we
present efficiency-improved interpolation techniques for the semicoherent
search stage. Via realistic simulations we demonstrate that overall these
optimizations can significantly lower the minimum detectable pulsed fraction by
almost 50% at the same computational expense.Comment: 22 pages, 13 figures; includes ApJ proof correction
Freud's Case Studies and the Locus of Psychoanalytic Knowledge
Reading through Sigmund Freud's case studies in chronological
order is a most instructive experience for anyone interested in the
intellectual history of psychoanalysis. One quickly sees, for example,
how Freud's technique evolved from the methodical and rather intrusive
attempts to dispel particular symptoms that we observe in Studies on
Hystem'a ( 1 895) to the method of free association that he describes in his
report on the case of Dora (1905). Or one sees how Freud's conception
of the transference developed, from the primitive notion of transference
as something to be avoided or dispelled, to the mature conception of
transference as the invaluable center of analysis, the very phenomenon
that has to be analyzed (again in the analysis of Dora). In this paper 1
shall review Freud's case studies with still another trajectory in mind:
how Freud's sense of the significance of his written case studies
themselves evolved. 1 shall show how his inital embarrassment over the
necessity of describing his cases in great detail was eventually supplanted
by a confidence that his case studies were important vehicles of
psychoanalytic knowledge. As his attitude changed, his initial anxiety
about how other medical and natural scientific readers would adjudicate
his cases was displaced by a willingness to assert delicate, tenuous
hypotheses in his cases, largely for the benefit of the psychoanalytic
community itself. And on a more abstract and perhaps less conscious
level, the positivistic belief in the importante of theory and the objective
verifiability of hypotheses that Freud had subscribed to from the time he had decided to study medicine was at least temporarily challenged by
another view of knowledge, a view that 1 shall try to clarify in this paper
Parameter-space metric of semicoherent searches for continuous gravitational waves
Continuous gravitational-wave (CW) signals such as emitted by spinning
neutron stars are an important target class for current detectors. However, the
enormous computational demand prohibits fully coherent broadband all-sky
searches for prior unknown CW sources over wide ranges of parameter space and
for yearlong observation times. More efficient hierarchical "semicoherent"
search strategies divide the data into segments much shorter than one year,
which are analyzed coherently; then detection statistics from different
segments are combined incoherently. To optimally perform the incoherent
combination, understanding of the underlying parameter-space structure is
requisite. This problem is addressed here by using new coordinates on the
parameter space, which yield the first analytical parameter-space metric for
the incoherent combination step. This semicoherent metric applies to broadband
all-sky surveys (also embedding directed searches at fixed sky position) for
isolated CW sources. Furthermore, the additional metric resolution attained
through the combination of segments is studied. From the search parameters (sky
position, frequency, and frequency derivatives), solely the metric resolution
in the frequency derivatives is found to significantly increase with the number
of segments.Comment: 14 pages, 5 figures (matching Phys.Rev.D version
Klimawandel: Internationaler Emissionshandel nach den Regeln des Kyoto-Protokolls
Die völkerrechtliche Vorlesung „ Internationaler Emissionshandel nach den Regeln des Kyoto- Protokolls“ - begleitet von einer Power Point Präsentation -stellt die These auf und führt den Nachweis, dass für den ab 01.Januar 2005 vorgesehenen Europäischen Emissionshandel sich ein faktisches völkerrechtlich verbindliches Normengefüge des Kyoto Protokolls von 1997 entwickelt hat, obwohl das Protokoll selbst im Januar 2004 noch nicht in Kraft getreten ist. Die Vorlesung fand auf Einladung im Bundesministerium für Wirtschaft und Arbeit am 22. Januar 2004 in Berlin statt, vor dem Deutsch-Bulgarischen Kooperationsrat, Arbeitsgruppe „ Energie“. Der Verfasser führt zur Sach-und Rechtslage aus: Insbesondere die sich häufenden und in ihrer Intensität weltweit zunehmenden Flutkatastrophen und wiederkehrenden tropischen Wirbelstürme hatten in der Europäischen Union und auf der Ebene ihrer Mitgliedstaaten die gesetzgeberischen Bemühungen um geeignete Vorsorgemaßnahmen im Klimaschutz weiter vorangetrieben, auch wenn das am 11. Dezember 1997 von der EU und ihren Mitgliedstaaten unterzeichnete Protokoll von Kyoto bislang noch nicht in Kraft getreten war -wegen der unentschlossenen Haltung des russischen Parlaments, der Ratifizierung des Protokolls zuzustimmen oder nicht. Vorgestellt werden die zentralen völkerrechtlich verbindlichen Rahmenvorschriften des Kyoto-Protokolls für die Schaffung und Funktion des internationalen Emissionshandels vor.Die Bedeutung, welche die völkerrechtli- chen Verpflichtungen aus dem Kyoto-Protokoll als rechtlich verbindlicher Rahmen für unternehmerische Entscheidungen in Rechtssicherheit und Planungssicherheit haben.Unschädlich für die Rechtssicherheit unternehmerischer Entscheidungen im Rahmen des kommenden europäischen Emissionshandelssystems sei, dass das Protokoll im Januar 2004 noch nicht in Kraft ist und es auch noch offen bleiben müsse, ob und wann das russische Parlament das Protokoll ratifizieren werde. Denn das EU-Richtlinienrecht habe sich der Regeln des Kyoto-Protokolls angenommen, indem das EU-Richtlinienrecht für den Raum der Europäischen Union ein Emissionshandelssystem nach Maßgabe des Kyoto-Protokolls verbindlich regele. Dargestellt werden die Funktionsweise des internationalen Emissionshandels sowie offene praktische Fragen von Bedeutung für einen funktionierenden internationalen Markt für den Handel mit Emissionsrechten. Beleuchtet wird die preispolitische Auswirkung, welche die im Januar 2004 noch ausstehende strategische Entscheidung Russlands auf den Weltmarkt der Emissionsrechte haben kann, wie Russland seine Emissionsrechte auf dem Markt einzusetzen gedenkt. Das Referat würdigt auch die bereits im Januar 2004 sich abzeichnende internationale Kritik am Kyoto-Protokoll und begrüsst, dass das Kyoto-Protokoll grundsätzlich nicht verworfen, sondern weiterhin für notwendig gehalten wird im Kampf gegen eine weitere Verschärfung des Klimawandels: das Protokoll bleibe zu ergänzen durch zusätzliche technische Vorsorgemaßnahmen auf nationaler Ebene in Weltregionen mit besonderem Gefährdungspotential exponierter Lagen von Küstenregionen wie z.B. in Bangladesh oder im gesamten karibischen Raum ,im Golf von Mexiko, an der Südküste der Vereinigten Staaten. Die Vorlesung erläutert schliesslich die flexiblen Instrumente des Kyoto-Protokolls, die für Unternehmen aus westlichen Industrieländern Bedeutung haben, die ihre Marktchancen mithilfe dieser Instrumente nutzen können: Sie können mithilfe sog. Joint Implementation Projekte Modernisierungsinvestitionen vornehmen. Gemeinsam mit Unternehmen der Energiewirtschaft in Ländern des Übergangs zur Marktwirtschaft in Mittel-, Ost-und Südosteuropa können Unternehmen aus Industrieländern Projekte zur Verbesserung der Energieeffizienz in Produktion, Verteilung und Verbrauch verwirklichen. Für die erzielte Verringerung von Emissionen erwerben investierende Unternehmen entsprechend anrechenbare Mengen von Gutschriften für Emissionsrechte. Diese aus Joint Implementation Projekten erzielten Gutschriften können investierende Unternehmen entweder für ihre eigene jährliche Emissionsbilanz verwenden oder aber mit dem Verkauf von überschüssigen Emissionsrechten die finanzielle Liquidität ihres Unternehmens verbessern . In der Praxis maßgebliche Investitionsbereiche werden angeführt
Freud's Case Studies and the Locus of Psychoanalytic Knowledge
Reading through Sigmund Freud's case studies in chronological
order is a most instructive experience for anyone interested in the
intellectual history of psychoanalysis. One quickly sees, for example,
how Freud's technique evolved from the methodical and rather intrusive
attempts to dispel particular symptoms that we observe in Studies on
Hystem'a ( 1 895) to the method of free association that he describes in his
report on the case of Dora (1905). Or one sees how Freud's conception
of the transference developed, from the primitive notion of transference
as something to be avoided or dispelled, to the mature conception of
transference as the invaluable center of analysis, the very phenomenon
that has to be analyzed (again in the analysis of Dora). In this paper 1
shall review Freud's case studies with still another trajectory in mind:
how Freud's sense of the significance of his written case studies
themselves evolved. 1 shall show how his inital embarrassment over the
necessity of describing his cases in great detail was eventually supplanted
by a confidence that his case studies were important vehicles of
psychoanalytic knowledge. As his attitude changed, his initial anxiety
about how other medical and natural scientific readers would adjudicate
his cases was displaced by a willingness to assert delicate, tenuous
hypotheses in his cases, largely for the benefit of the psychoanalytic
community itself. And on a more abstract and perhaps less conscious
level, the positivistic belief in the importante of theory and the objective
verifiability of hypotheses that Freud had subscribed to from the time he had decided to study medicine was at least temporarily challenged by
another view of knowledge, a view that 1 shall try to clarify in this paper
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