On the gauge fixing in the Hamiltonian analysis of general teleparallel theories

The covariant formulation of teleparallel gravity theories must include the spin connection, which has 6 degrees of freedom. One can, however, always choose a gauge such that the spin connection is put to zero. In principle this gauge may affect counting of degrees of freedom in the Hamiltonian analysis. We show for general teleparallel theories of gravity, that fixing the gauge such that the spin connection vanishes in fact does not affect the counting of degrees of freedom. This manifests in the fact that the momenta of the Lorentz transformations which generate the spin connection are fully determined by the momenta of the tetrads.Comment: 8 pages, no figures, Contribution to the proceedings of the conference "Teleparallel Universes" in Salamanc

Some Early Geologists and Their Work in Montana

This paper marks an increased refinement and more detailed accuracy in the description of the geological features of the state. It includes the recent studies of mineral deposits, of oil structures, of the formations of bedded rocks and their included fossils, carried on both by the Federal and State governments and by various interested private persons, such as the mining companies. It is within this period that the Federal Government encouraged the U. S. Geological Survey in the publication of monographs on the National Parks, papers of great popular interest and educational value making these beautiful regions comprehensible in their geological features to the touring public

Combined EISCAT radar and optical multispectral and tomographic observations of black aurora

Black auroras are recognized as spatially well-defined regions within a uniform diffuse auroral background where the optical emission is significantly reduced. Black auroras typically appear post-magnetic midnight and during the substorm recovery phase, but not exclusively so. We report on the first combined multimonochromatic optical imaging, bistatic white-light TV recordings and incoherent scatter radar observations of black aurora by EISCAT of the phenomenon. From the relatively larger reduction in luminosity at 4278 Å than at 8446 Å we show that nonsheared black auroras are most probably not caused by downward directed electrical fields at low altitude. From the observations, we determine this by relating the height and intensity of the black aurora to precipitating particle energy within the surrounding background diffuse aurora. The observations are more consistent with an energy selective loss cone. Hence the mechanism causing black aurora is most probably active in the magnetosphere rather than close to Earth

Magnetospheric signatures of ionospheric density cavities observed by cluster

AJBR ackowledges support from STFC under consolidated grant ST/K000993/1.We present Cluster measurements of large amplitude electric fields corre- lated with intense downward field-aligned currents, observed during a nightside crossing of the auroral zone. The data are reproduced by a simple model of magnetosphere-ionosphere coupling which, under different conditions, can also produce a divergent electric field signature in the downward current region, or correlation between the electric and perturbed magnetic fields. We conclude that strong electric field associated with intense downward field-aligned current, such as this observation, is a signature of ionospheric plasma depletion caused by the downward current. It is also shown that the electric field in the downward current region correlates with downward current density if a background field is present, e.g. due to magnetospheric convection.Publisher PDFPeer reviewe

Chemoenzymatic Probes for Detecting and Imaging Fucose-α(1-2)-galactose Glycan Biomarkers

The disaccharide motif fucose-α(1-2)-galactose (Fucα(1-2)Gal) is involved in many important physiological processes, such as learning and memory, inflammation, asthma, and tumorigenesis. However, the size and structural complexity of Fucα(1-2)Gal-containing glycans have posed a significant challenge to their detection. We report a new chemoenzymatic strategy for the rapid, sensitive detection of Fucα(1-2)Gal glycans. We demonstrate that the approach is highly selective for the Fucα(1-2)Gal motif, detects a variety of complex glycans and glycoproteins, and can be used to profile the relative abundance of the motif on live cells, discriminating malignant from normal cells. This approach represents a new potential strategy for biomarker detection and expands the technologies available for understanding the roles of this important class of carbohydrates in physiology and disease

Interferometric radar observations of filamented structures due to plasma instabilities and their relation to dynamic auroral rays

International audienceSeveral explanations have been proposed for Naturally Enhanced ion-acoustic Echoes observed at mid- and high-latitude Incoherent Scatter observatories. A decisive measure for distinguishing between these explanations is whether or not simultaneously observed up- and down-shifted enhancement occur simultaneously, or if they are the result of temporal and/or spatial averaging. The EISCAT Svalbard Radar has two antennas in the same radar system, which can be used as an interferometer when pointed parallel. In observations from 17 January 2002, between 06:46:10 and 06:46:30 UT, we used this possibility, in combination with direct sampling of the received signals, to yield measurements of "naturally enhanced ion-acoustic echoes" with sufficiently high resolution to resolve such averaging, if any. For the first time, radar interferometry has been employed to estimate the sizes of coherent structures. The observations were coordinated with an image intensified video camera with a narrow field of view. Together, this forms the initial study on the causal relationships between enhanced echoes and fine structure in the auroral activity on sub-kilometer, sub-second scales. The results confirm that the enhanced echoes originate from very localised regions (~300m perpendicular to the magnetic field at 500km altitude) with varying range distribution, and with high time variability (?200ms). The corresponding increase in scattering cross section, up to 50dB above incoherent scattering, eliminates theoretical explanations based on marginal stability. The simultaneously observed up- and down-shifted enhanced shoulders, when caused by sufficiently narrow structures to be detected by the interferometer technique, originate predominantly from the same volume. These results have significant impact on theories attempting to explain the enhancements, in particular it is found that the ion-electron two-stream mechanism favoured by many authors is an unlikely candidate to explain the observations. The video data has helped establish a clear correlation between the enhanced echoes and auroral activity, on sub-second time scales, showing a threshold connection between the auroral intensity and the triggering of the radar enhancements. It appears that the up- and down-shifted enhanced echoes correlate with fine auroral structures in different ways. Key words. Ionosphere (auroral ionosphere; plasma waves and instabilities) ? Radio science (interferometry

Phase calibration of the EISCAT Svalbard Radar interferometer using optical satellite signatures

The link between natural ion-line enhancements in radar spectra and auroral activity has been the subject of recent studies but conclusions have been limited by the spatial and temporal resolution previously available. The next challenge is to use shorter sub-second integration times in combination with interferometric programmes to resolve spatial structure within the main radar beam, and so relate enhanced filaments to individual auroral rays. This paper presents initial studies of a technique, using optical and spectral satellite signatures, to calibrate the received phase of a signal with the position of the scattering source along the interferometric baseline of the EISCAT Svalbard Radar. It is shown that a consistent relationship can be found only if the satellite passage through the phase fringes is adjusted from the passage predicted by optical tracking. This required adjustment is interpreted as being due to the vector between the theoretical focusing points of the two antennae, i.e. the true radar baseline, differing from the baseline obtained by survey between the antenna foot points. A method to obtain a measurement of the true interferometric baseline using multiple satellite passes is outlined

Problematic Men and Restricted Women: A Discourse Analysis on Swedish Feminism

Feminism is everywhere: in all sorts of media, in fashion, in entertainment, and in politics. By focusing on social media, this thesis examines how self-identified feminists construct feminism in Sweden. The construction is found in a popular Swedish feminist podcast, a debate on the premises of sisterhood, a women’s separatist Facebook group, and an interview with the second wave feminist Agnes Wold. Drawing on Laclau and Mouffe’s discourse theory and Carol Bacchi’s policy analysis, What’s the Problem Represented to be, this thesis examines how the hegemonic feminism is constructed across the identified discourses. These discourses, one of problematic men and one of restricted women, exist in relation to each other and contain the notion that men are a problem that affects women’s living conditions. With regard to what it excludes, the hegemonic feminism is heteronormative and constructed from the perspectives of the self-identified feminists. The discourse analysis also shows that the feminists protect and care for other women solely because they are women

Kovariantsete teleparalleelsete gravitatsiooniteooriate Hamiltoni analüüs

Möödunud sajandil valitses maailmapilt et gravitatsiooni kirjeldab jõuteooria asemel Üldrelatiivsusteooria, mille raames mateeria mõjub aegruumi geomeetriat milles me elame. Eelmainitud kirjeldus on tõestanud oma sobivust paljudes eksperimentaalsetes ja vaatuslikes testides alates Albert Einsteini gravitatsiooniteooria püstitamisest. Lisaks on ta oma edukust näidanud kosmoloogilise standardmudeli lahendamatu osana. Sellest hoolimata on kaasaegsed vaatlused avaldanud statistiliselt märkamisväärseid pingeid kosmoloogilises standardmudelis. Lisaks koosneb 95% universumi mateeriasisust seni selgitamatuks jäänud tumeainest ja tumeenergiast. Nende probleemide käsitlemiseks on võimalik uurida modifitseeritud gravitatsiooniteooriaid. Selles väitekirjas on uuritud modifitseeritud teleparalleelsed gravitatsiooniteooriad. Need teooriad lähtuvad arusaamast et Üldrelatiivsusteooriat on võimalik kirjeldada füüsikaliiselt ekvivalentsel viisil. Siiski näitab teleparalleelne kirjeldus ette uusi võimalusi gravitatsiooniteooria modifitseerida. Väitekirjas on lähemalt uuritud f (TNGR ) gravitatsiooniteooria ja käsitletud küsimus kas f (TNGR ) on teoreetilise vaatenurga alt kooskõlaline gravitatsiooniteooria. Selle küsimusele vastamiseks rakendati teooriale esmakordselt kovariantset Hamiltoni formalismi. See käsitlus on fundamentaalsel perspektiivil asjakohasem ja üldisem ning annab võimalust jõuda erinevate järeldusteni võrreldes kirjanduses levinud käsitlusega. f (TNGR ) teooria Hamiltoni analüüsi esimene osa on konkreetselt tuletatud. Käsitletud lähenemine avab teed kõige populaarsemate teleparalleelsete gravitatsiooniteooriate kanoonilisele Hamiltoni analüüsile. Väitekirja peamine järeldus näitab et f (TNGR ) teooria on tõsiselt kahtlustav, kuid on veel mõned aspektid mis on väärt uurida enne kui f (TNGR ) teooria on täielikult välistatud kui kooskõlaline gravitatsiooniteooria.For over a century, it has been known that gravity should be described by the theory of general relativity, in which matter is affecting the spacetime geometry we live in, rather than as a force theory. This description has been proven to pass much experimental and observational tests since Albert Einstein formulated this theory of gravity. Furthermore, it has been proven successful as incorporated in the standard model of cosmology. However, recently it has become evident from observation that there are statistically significant tensions in observations within the standard model of cosmology. Furthermore, 95% of our universe consists of dark matter and dark energy, which is still not understood. In order to address these issues one may look into modified theories of gravity. In this thesis teleparallel modified theories of gravity are examined. They make use of the fact that there are alternative physically equivalent descriptions of general relativity. However, the teleparallel formulation admits new ways to modify gravity. In particular a theory called f (TNGR )-gravity is examined. The question this thesis address is if f (TNGR )-gravity is viable as a theory from a theoretical point of view. In order to answer this question the so-called covariant Hamiltonian analysis of the theory is considered for the first time. This theory is more correct and general from a fundamental perspective and it might lead to different conclusions than for those found in the literature. The first part in the Hamiltonian analysis for f (TNGR )-gravity is explicitly derived. This paves the way for a canonical Hamiltonian analysis for the most popular theories of teleparallel gravity. The main conclusion of the thesis is that the viability of f (TNGR )-gravity is in serious doubt. Though, there are still a few points that need to be examined before ruling out f (TNGR ) as a viable theory of gravity.https://www.ester.ee/record=b545040