Non-relativistic limit of multidimensional gravity: exact solutions and applications

It is found the exact solution of the Poisson equation for the multidimensional space with topology $M_{3+d}=\mathbb{R}^3\times T^d$. This solution describes smooth transition from the newtonian behavior $1/r_3$ for distances bigger than periods of tori (the extra dimension sizes) to multidimensional behavior $1/r^{1+d}_{3+d}$ in opposite limit. In the case of one extra dimension $d=1$, the gravitational potential is expressed via compact and elegant formula. These exact solutions are applied to some practical problems to get the gravitational potentials for considered configurations. Found potentials are used to calculate the acceleration for point masses and gravitational self-energy.It is proposed models where the test masses are smeared over some (or all) extra dimensions. In 10-dimensional spacetime with 3 smeared extra dimensions, it is shown that the size of 3 rest extra dimensions can be enlarged up to submillimeter for the case of 1TeV fundamental Planck scale $M_{Pl(10)}$. In the models where all extra dimensions are smeared, the gravitational potential exactly coincides with the newtonian one regardless of size of the extra dimensions. Nevertheless, the hierarchy problem can be solved in these models.Comment: LaTex file, 18 pages, 4 figure

Measurement of mechanical losses in the carbon nanotube black coating of silicon wafers

The successful detection of gravitational waves from astrophysical sources carried out by the laser interferometric detectors LIGO and Virgo have stimulated scientists to develop a new generation of more sensitive gravitational wave detectors. In the proposed upgrade called LIGO Voyager, silicon test masses will be cooled to cryogenic temperatures. To provide heat removal from the test masses when they absorb the laser light one can increase their thermal emissivity using a special black coating. We have studied mechanical losses in a carbon nanotube black coating deposited on silicon wafers. The additional thermal noise associated with mechanical loss in this coating was calculated using a value of the product of the coating Young's modulus and the coating mechanical loss angle determined from the measurements. It was found that at temperatures of about 123 K, the additional thermal noise of the LIGO Voyager test mass caused by the carbon nanotube black coating deposited on its barrel is less than the noise associated with the Acktar Black coating and is 20 times less than the noise due to the optical high reflective (HR) coating of the test mass

Resonant Cyclotron Radiation Transfer Model Fits to Spectra from Gamma-Ray Burst GRB870303

We demonstrate that models of resonant cyclotron radiation transfer in a strong field (i.e. cyclotron scattering) can account for spectral lines seen at two epochs, denoted S1 and S2, in the Ginga data for GRB870303. Using a generalized version of the Monte Carlo code of Wang et al. (1988,1989b), we model line formation by injecting continuum photons into a static plane-parallel slab of electrons threaded by a strong neutron star magnetic field (~ 10^12 G) which may be oriented at an arbitrary angle relative to the slab normal. We examine two source geometries, which we denote "1-0" and "1-1," with the numbers representing the relative electron column densities above and below the continuum photon source plane. We compare azimuthally symmetric models, i.e. models in which the magnetic field is parallel to the slab normal, with models having more general magnetic field orientations. If the bursting source has a simple dipole field, these two model classes represent line formation at the magnetic pole, or elsewhere on the stellar surface. We find that the data of S1 and S2, considered individually, are consistent with both geometries, and with all magnetic field orientations, with the exception that the S1 data clearly favor line formation away from a polar cap in the 1-1 geometry, with the best-fit model placing the line-forming region at the magnetic equator. Within both geometries, fits to the combined (S1+S2) data marginally favor models which feature equatorial line formation, and in which the observer's orientation with respect to the slab changes between the two epochs. We interpret this change as being due to neutron star rotation, and we place limits on the rotation period.Comment: LaTeX2e (aastex.cls included); 45 pages text, 17 figures (on 21 pages); accepted by ApJ (to be published 1 Nov 1999, v. 525

Electrodynamics of Magnetars: Implications for the Persistent X-ray Emission and Spindown of the Soft Gamma Repeaters and Anomalous X-ray Pulsars

(ABBREVIATED) We consider the structure of neutron star magnetospheres threaded by large-scale electrical currents, and the effect of resonant Compton scattering by the charge carriers (both electrons and ions) on the emergent X-ray spectra and pulse profiles. In the magnetar model for the SGRs and AXPs, these currents are maintained by magnetic stresses acting deep inside the star. We construct self-similar, force-free equilibria of the current-carrying magnetosphere with a power-law dependence of magnetic field on radius, B ~ r^(-2-p), and show that a large-scale twist softens the radial dependence to p < 1. The spindown torque acting on the star is thereby increased in comparison with a vacuum dipole. We comment on the strength of the surface magnetic field in the SGR and AXP sources, and the implications of this model for the narrow measured distribution of spin periods. A magnetosphere with a strong twist, B_\phi/B_\theta = O(1) at the equator, has an optical depth ~ 1 to resonant cyclotron scattering, independent of frequency (radius), surface magnetic field strength, or charge/mass ratio of the scattering charge. When electrons and ions supply the current, the stellar surface is also heated by the impacting charges at a rate comparable to the observed X-ray output of the SGR and AXP sources, if B_{dipole} ~ 10^{14} G. Redistribution of the emerging X-ray flux at the ion and electron cyclotron resonances will significantly modify the emerging pulse profile and, through the Doppler effect, generate a non-thermal tail to the X-ray spectrum. The sudden change in the pulse profile of SGR 1900+14 after the 27 August 1998 giant flare is related to an enhanced optical depth to electron cyclotron scattering, resulting from a sudden twist imparted to the external magnetic field.Comment: 31 January 2002, minor revisions, new section 5.4.

Gamma Ray Bursts from the Evolved Galactic Nuclei

A new cosmological scenario for the origin of gamma ray bursts (GRBs) is proposed. In our scenario, a highly evolved central core in the dense galactic nucleus is formed containing a subsystem of compact stellar remnants (CSRs), such as neutron stars and black holes. Those subsystems result from the dynamical evolution of dense central stellar clusters in the galactic nuclei through merging of stars, thereby forming (as has been realized by many authors) the short-living massive stars and then CSRs. We estimate the rate of random CSR collisions in the evolved galactic nuclei by taking into account, similar to Quinlan & Shapiro (1987), the dissipative encounters of CSRs, mainly due to radiative losses of gravitational waves, which results in the formation of intermediate short-living binaries, with further coalescence of the companions to produce GRBs. We also consider how the possible presence of a central supermassive black hole, formed in a highly evolved galactic nucleus, influences the CSR binary formation. This scenario does not postulate ad hoc a required number of tight binary neutron stars in the galaxies. Instead, it gives, for the most realistic parameters of the evolved nuclei, the expected rate of GRBs consistent with the observed one, thereby explaining the GRB appearance in a natural way of the dynamical evolution of galactic nuclei. In addition, this scenario provides an opportunity for a cosmological GRB recurrence, previously considered to be a distinctive feature of GRBs of a local origin only. We also discuss some other observational tests of the proposed scenario.Comment: 25 pages, LATEX, uses aasms4.sty, accepted by Ap

ПАЛЕОПРОТЕРОЗОЙСКАЯ ИМАНДРА-ВАРЗУГСКАЯ РИФТОГЕННАЯ СТРУКТУРА (КОЛЬСКИЙ ПОЛУОСТРОВ): ИНТРУЗИВНЫЙ МАГМАТИЗМ И МИНЕРАГЕНИЯ

The article provides data on the structure of the Paleoproterozoic intercontinental Imandra-Varzuga rifting structure (IVS) and compositions of intrusive formations typical of the early stage of the IVS development and associated mineral resources. IVS is located in the central part of the Kola region. Its length is about 350 km, and its width varies from 10 km at the flanks to 50 km in the central part. IVS contains an association of the sedimentary-volcanic, intrusive and dyke complexes. It is a part of a large igneous Paleoproterozoic province of the Fennoscandian Shield spreading for a huge area (about 1 million km2), which probably reflects the settings of the head part of the mantle plume. Two age groups of layered intrusions were associated with the initial stage of the IVS development. The layered intrusions of the Fedorovo-Pansky and Monchegorsk complexes (about 2.50 Ga) are confined to the northern flank and the western closure of IVS, while intrusions of the Imandra complex (about 2.45 Ga) are located at the southern flank of IVS. Intrusions of older complexes are composed of rock series from dunite to gabbro and anorthosites (Monchegorsk complex) and from orthopyroxenite to gabbro and anorthosites (Fedorovo-Pansky complex). Some intrusions of this complexes reveal features of multiphase ones. The younger Imandra complex intrusions (about 2.45 Ga) are stratified from orthopyroxenite to ferrogabbro. Their important feature is comagmatical connection with volcanites. All the intrusive complexes have the boninite-like mantle origin enriched by lithophyle components. Rocks of these two complexеs with different age have specific geochemical characteristics. In the rocks of the Monchegorsk and Fedorovo-Pansky complexes, the accumulation of REE clearly depends on the basicity of the rocks, the spectrum of REE is non-fractionated and ‘flat’, and the Eu positive anomaly is slightly manifested. In the rocks of the Imandra complex, the level of REE accumulation is relatively higher. The spectrum of REE here differs with more fractionated LREE with a ‘flat’ distribution of HREE and distinct Eu anomalies. Rocks of all the intrusive complexes are characterized mostly by negative eNd(T) values, and eNd values are distributed more heterogeneously in the rocks of the Monchegorsk complex than in the rocks of the Fedorovo-Pansky complex. Deposits and occurrences of Cr, complex PGE-Cu-Ni and low-sulfide Pt-Pd ores of the world class are spatially related and genetically associated with the IVS intrusive complexes. The Sopcheozero deposit (Monchepluton of the Monchegorsk complex) and Bolshaya Varaka deposit (the same-name intrusion of the Imandra complex) represent a layered Cr mineralization. Complex PGE-Cu-Ni deposits are confined to Monchepluton. They occur in vein ores of the Nittis-Kumuzhya-Travyanaya massifs (which have been worked out) and Sopcha, vein PGE-Cu, injecting Ni ores mostly and bottom deposits of the Nittis-Kumuzhya-Travyanaya massifs, as well as in the Nyud ‘critical’ horizon. In the past 10–15 years, low-sulphide Pt-Pd ores were discovered as new for the Kola region. Two main types of such ores have been distinguished: (1) stratiform (rift) ores being consistent with the massifs’ layering, and (2) basal ores located within lower marginal zones. Deposits of Kievey (West-Pansky massif of the Fedorovo-Pansky complex), horizon 330 of the Sopcha and Vurechuayvench (Monchepluton of the Monchegorsk complex) belong to the first type; the second type is represented by the Fedorovotundrovskoe (Fedorovo-Pansky complex), South Sopcha and Loypishnyun (Mon­chetundrovsky massif of Monchegorsk complex) deposits.   В статье приведены данные о строении палеопротерозойской внутриконтинентальной Имандра-Варзуг­ской рифтогенной структуры (ИВС), составе интрузивных образований ее раннего этапа развития и связанных с ними полезных ископаемых. ИВС расположена в центральной части Кольского региона, имеет протяженность около 350 км и ширину от 10 км на флангах до 50 км в центральной части и включает ассоциацию осадочно-вулканоген­ных, интрузивных и дайковых комплексов. Она входит в состав обширной изверженной палеопротерозойской провинции Фенноскандинавского щита, которая охватывает огромный площадной ареал развития (около 1 млн км2), отражающий, по-видимому, параметры головной части мантийного плюма. С начальным этапом развития ИВС свя­зано формирование двух возрастных групп расслоенных интрузий. К северному борту и западному замыканию структуры приурочены расслоенные интрузии Федорово-Панского и Мончегорского комплексов с возрастом около 2.50 млрд лет, а к южному борту структуры – интрузии Имандровского комплекса с возрастом около 2.45 млрд лет. Интрузии более древних комплексов образованы рядом пород от дунитов до габбро и анортозитов (Мончегорский комплекс) и от ортопироксенитов до габбро и анортозитов (Федорово-Панский комплекс). При этом в некоторых интрузиях этих комплексов установлены признаки их многофазности. Интрузии более молодого Имандровского комплекса с возрастом около 2.45 млрд лет расслоены от ортопироксенитов до феррогаббро. Важной их особенностью является комагматическая связь с вулканитами. Все интрузивные комплексы образованы из бонинитоподобного мантийного источника, обогащенного литофильными компонентами. Для пород этих двух разновозрастных комплексов характерны свои отличительные геохимические особенности. В породах Мончегорского и Федорово-Пан­ского комплексов наблюдается отчетливая зависимость накопления редкоземельных элементов (РЗЭ) от основности пород, нефракционированный «плоский» характер спектра РЗЭ и незначительно проявленные положительные Eu аномалии. В породах Имандровского комплекса уровень накопления РЗЭ сравнительно более высокий. Спектр РЗЭ в них отличается более фракционированным характером легких редкоземельных элементов (РЗЭ) при «плоском» распределении тяжелых редкоземельных элементов (РЗЭ) и отчетливо выраженными Eu аномалиями. Породы всех интрузивных комплексов характеризуются преимущественно отрицательными значениями параметра eNd(T), при этом в породах Мончегорского комплекса распределение значений eNd более гетерогенное, чем в породах Федорово-Панского комплекса. С интрузивными комплексами ИВС пространственно и генетически связаны месторождения и проявления Cr, комплексных платинометально (ЭПГ)-Cu-Ni и малосульфидных Pt-Pd руд мирового уровня. Стратиформное хромовое оруденение представлено Сопчеозерским месторождением (Мончеплутон Мончегорского комплекса) и месторождением Большая Варака (одноименная интрузия Имандровского комплекса). Комплексные ЭПГ-Cu-Ni месторождения – приурочены к Мончегорскому плутону. Они присутствуют в жильных рудах массивов Ниттис-Кумужья-Травяная (отработаны) и Сопчи, жильных ЭПГ – Cu, инъекционных существенно Ni рудах и донной залежи массива Ниттис-Кумужья-Травяная, а также в «критическом» горизонте Нюда. Малосульфидные Pt-Pd руды были выявлены в течение последних 10–15 лет и являются новыми для Кольского региона. Они делятся на два основных типа: стратиформные (рифовые), гармоничные с расслоенностью массивов, и базальные, локализованные в пределах нижних краевых зон. К первому типу относятся месторождения Киевей (Западно-Панский массив Федорово-Панского комплекса), 330-го горизонта Сопчи и Вурэчуайвенч (Мончеплутон Мончегорского комплекса), ко второму – Федоровотундровское (Федорово-Панский комплекс), Южносопчинское и Лойпишнюн (Мончетундровский массив Мончегорского комплекса). 

Comparison of Image Restoration Methods for Lunar Epithermal Neutron Emission Mapping

Orbital measurements of neutrons by the Lunar Exploring Neutron Detector (LEND) onboard the Lunar Reconnaissance Orbiter are being used to quantify the spatial distribution of near surface hydrogen (H). Inferred H concentration maps have low signal-to-noise (SN) and image restoration (IR) techniques are being studied to enhance results. A single-blind. two-phase study is described in which four teams of researchers independently developed image restoration techniques optimized for LEND data. Synthetic lunar epithermal neutron emission maps were derived from LEND simulations. These data were used as ground truth to determine the relative quantitative performance of the IR methods vs. a default denoising (smoothing) technique. We review and used factors influencing orbital remote sensing of neutrons emitted from the lunar surface to develop a database of synthetic "true" maps for performance evaluation. A prior independent training phase was implemented for each technique to assure methods were optimized before the blind trial. Method performance was determined using several regional root-mean-square error metrics specific to epithermal signals of interest. Results indicate unbiased IR methods realize only small signal gains in most of the tested metrics. This suggests other physically based modeling assumptions are required to produce appreciable signal gains in similar low SN IR applications

Graviton Production By Two Photon and Electron-Photon Processes In Kaluza-Klein Theories With Large Extra Dimensions

We consider the production of gravitons via two photon and electron-photon fusion in Kaluza-Klein theories which allow TeV scale gravitational interactions. We show that at electron-positron colliders, the processes l+l- -> l+ l- graviton, with l=e, mu, can lead to a new signal of low energy gravity of the form l+l- -> l+l- + missing energy which is well above the Standard Model background. For example, with two extra dimensions at the Next Linear Collider with a center of mass energy of 500 or 1000 GeV, hundreds to thousands such l+ l- graviton events may be produced if the scale of the gravitational interactions, M_D, is around a few TeV. At a gamma-electron collider, more stringent bounds may be placed on M_D via the related reaction e^-\gamma -> e^- graviton. For instance, if a 1TeV electron positron collider is converted to an electron-photon collider, a bound of ~10TeV may be placed on the scale M_D if the number of extra dimensions delta=2 while a bound of ~4TeV may be placed if delta=4.Comment: 25 pages 6 figures, minor changes made in the text and changes in reference