Exotic Entities Research Articles

Manifestly covariant worldline actions from coadjoint orbits. Part I. Generalities and vectorial descriptions

We derive manifestly covariant actions of spinning particles starting from coadjoint orbits of isometry groups, by using Hamiltonian reductions. We show that the defining conditions of a classical Lie group can be treated as Hamiltonian constraints which generate the coadjoint orbits of another, dual, Lie group. In case of (inhomogeneous) orthogonal groups, the dual groups are (centrally-extended inhomogeneous) symplectic groups. This defines a symplectic dual pair correspondence between the coadjoint orbits of the isometry group and those of the dual Lie group, whose quantum version is the reductive dual pair correspondence à la Howe. We show explicitly how various particle species arise from the classification of coadjoint orbits of Poincaré and (A)dS symmetry. In the Poincaré case, we recover the data of the Wigner classification, which includes continuous spin particles, (spinning) tachyons and null particles with vanishing momenta, besides the usual massive and massless spinning particles. In (A)dS case, our classification results are not only consistent with the pattern of the corresponding unitary irreducible representations observed in the literature, but also contain novel information. In dS, we find the presence of partially massless spinning particles, but continuous spin particles, spinning tachyons and null particles are absent. The AdS case shows the largest diversity of particle species. It has all particles species of Poincaré symmetry except for the null particle, but allows in addition various exotic entities such as one parameter extension of continuous particles and conformal particles living on the boundary of AdS. Notably, we also find a large class of particles living in “bitemporal” AdS space, including ones where mass and spin play an interchanged role. We also discuss the relative inclusion structure of the corresponding orbits.

The Astrobiology of Alien Worlds: Known and Unknown Forms of Life

Most definitions of life assume that, at a minimum, life is a physical form of matter distinct from its environment at a lower state of entropy than its surroundings, using energy from the environment for internal maintenance and activity, and capable of autonomous reproduction. These assumptions cover all of life as we know it, though more exotic entities can be envisioned, including organic forms with novel biochemistries, dynamic inorganic matter, and self-replicating machines. The probability that any particular form of life will be found on another planetary body depends on the nature and history of that alien world. So the biospheres would likely be very different on a rocky planet with an ice-covered global ocean, a barren planet devoid of surface liquid, a frigid world with abundant liquid hydrocarbons, on a rogue planet independent of a host star, on a tidally locked planet, on super-Earths, or in long-lived clouds in dense atmospheres. While life at least in microbial form is probably pervasive if rare throughout the Universe, and technologically advanced life is likely much rarer, the chance that an alternative form of life, though not intelligent life, could exist and be detected within our Solar System is a distinct possibility.

New records of exotic species of Oniscidea (Crustacea: Isopoda) from northern Mexico

To date 86 species of 33 genera and 16 families of Oniscidea have been recorded in Mexico. Collections of 4 academic institutions and recent field materials were revised. From 1,820 specimens, 1,417 (77.6%) were determined to belong to 6 exotic forms. A taxonomic account and a species identification key with SEM plates of these exotic entities are presented. For morphological analysis we used light and SEM microscopy. The molecular identity of 5 of the 6 forms was examined through cytochrome oxidase 1 gene (mtDNA) analyses. The exotic species determined are: Armadillidae, Cubaris murina; Armadillidiidae, Armadillidium vulgare; Porcellionidae, Agabiformius lentus, Porcellio laevis, P. scaber, and Porcellionides pruinosus. The exotic oniscideans were recorded from urban, rural and natural (riparian) zones in 15 states of northern Mexico, including the first formal records in Aguascalientes,Chihuahua, Durango, and Zacatecas. Armadillidium vulgare, P. laevis, and P. pruinosus often co-occurred and are the most widely distributed species in this region. Although most of the material examined was recorded from urban zones(> 50% of studied sites), A. vulgare and P. laevis were also found in riparian areas (natural zones), yet P. pruinosus was recorded mainly from riparian areas (60% of 45 lots examined).

Mesoarchean TTG magmatism from the northeastern margin of the Kaapvaal Craton, southern Africa: Arguments for an exotic terrane (remnant of Pilbara Craton?)

High-grade terranes along Archean cratonic margins either represent remobilized equivalents of the adjacent low-grade domain or an exotic entity which accreted to the developing craton. This study addresses this debate for the Southern Marginal Zone high-grade terrane along the northeastern margin of the Kaapvaal Craton. The Hout River shear zone separates the high-grade terrane from the adjacent low-grade Pietersburg block of the Kaapvaal Craton. Tonalite-trondhjemites of the Baviaanskloof gneiss unit constitute the dominant rock in the Southern Marginal Zone. Both pyroxene-bearing and pyroxene-absent variants occur. Locally, the granitoids are affected by anatectic and metasomatic overprints. Magmatic textures are better preserved in the massive granitoids. U-Pb zircon analyses of two orthopyroxene-bearing granitoids gave Mesoarchean crystallization ages [3088 ± 11 Ma (massive), 3121 ± 9 Ma (banded)]. However, overprint ages differ, with 2706 + 50/−34 Ma from the massive variety, and 1925 ± 19 Ma, 1976 ± 11 Ma from the banded variety. The syn-tectonic ~2.71 Ga is interpreted as metamorphic overprint age, while the post-tectonic ~2 Ga represent age of local overprint. Available geochemical data on the Baviaanskloof granitoids are similar to Archean TTGs. A possible spatial-temporal transition from ~3.13 Ga low-pressure through ~3.12–2.98 Ga medium-pressure to ~2.92 Ga high-pressure TTG is delineated from the northwest towards the southeastern Southern Marginal Zone. This trend is compatible with the southward directed polarity of accretion events recognised in the adjacent low-grade Pietersburg block. We argue that the northeastern margin of the Kaapvaal Craton, north of the Hout River shear zone, is an exotic terrane because 1) the Baviaanskloof granitoid event (~3.1–2.9 Ga with peak at ~3.1 Ga) is older than the accretion episodes (~2.97–2.92 Ga with peak at ~2.95 Ga, and ~2.87–2.84 Ga with peak at ~2.86 Ga) in the adjacent Pietersburg block, 2) the younger ~2.86 Ga event occurs closer to the Hout River shear zone, while the older ~2.95 Ga event was away from it, and 3) contemporaneous (~3.1–3.0 Ga) detrital zircons are absent in greenstone belts of the Pietersburg block that are proximal to the Hout River shear zone. Possible connection to rocks of similar age from the Pilbara Craton as part of the Vaalbara supercraton is explored.

Exploring the myrmecofauna of Sicily: thirty-two new ant species recorded, including six new to Italy and many new aliens (Hymenoptera, Formicidae)

Abstract As a result of recent collecting efforts and older unpublished data of one of us (AA), 32 ant species (including 2 morphospecies) new to the island of Sicily (Italy) were discovered. Seven of these taxa represent unequivocally exotic entities, whose discovery marks a decisive increase of this component in the local fauna. Among these, two forms of Nylanderia EMERY, 1906 are treated as morphospecies because of the problematic taxonomy of the genus. Six taxa among the discovered species are entirely new to the myrmecofauna of Italy. Finally, Tetramorium indocile SANTSCHI, 1927 is reported for the first time as a host for the social parasite Strongylognathus testaceus (SCHENCK, 1852). The state of the art of the Sicilian myrmecofauna, now counting about 150 species, is commented on.

Genesis of the Archean–Paleoproterozoic Tabletop Domain, Rudall Province, and its endemic relationship to the West Australian Craton

ABSTRACTThe Tabletop Domain of the Rudall Province has been long thought an exotic entity to the West Australian Craton. Recent re-evaluation of this interpretation suggests otherwise, but is founded on limited data. This study presents the first comprehensive, integrated U–Pb geochronology and Hf-isotope analysis of igneous and metasedimentary rocks from the Tabletop Domain of the eastern Rudall Province. Field observations, geochronology and isotope results confirm an endemic relationship between the Tabletop Domain and the West Australian Craton (WAC), and show that the Tabletop Domain underwent a similar Archean–Paleoproterozoic history to the western Rudall Province. The central Tabletop Domain comprises Archean–Paleoproterozoic gneissic rocks with three main age components. Paleo–Neoarchean (ca 3400–2800 Ma) detritus is observed in metasedimentary rocks and was likely sourced from the East Pilbara Craton. Protoliths to mafic gneiss and metasedimentary rocks are interpreted to have been emplaced and deposited during the early Paleoproterozoic (ca 2400–2300 Ma), and exhibit age and isotopic affinities to the Capricorn Orogen basement (Glenburgh Terrane). Mid–late Paleoproterozoic mafic and felsic magmatism (ca 1880–1750 Ma) is assigned to the Kalkan Supersuite, which is exposed in the western Rudall Province. The Kalkan Supersuite provided the main source of detritus for mid–late Paleoproterozoic metasedimentary rocks in the Tabletop Domain. Similarities in the age and Hf-isotope compositions of detrital zircon from these metasedimentary rocks and Capricorn Orogeny basin sediments suggests that a regionally extensive, linked basin system may have spanned the northern WAC at this time. The Tabletop Domain records evidence for two metamorphic events. Mid–late Paleoproterozoic deformation (ca 1770–1750 Ma) was high-grade, regional and involved the development of gneissic fabrics. In contrast, early Mesoproterozoic (ca 1580 Ma) high-grade deformation was localised and associated with more widespread, late-stage, greenschist facies alteration. These new findings highlight that the Tabletop Domain experienced a much higher grade of deformation than previously assumed, with a Paleoproterozoic metamorphic history similar to that of the western Rudall Province.

An exotic Mesoarchean microcontinent: The Coorg Block, southern India

Sandwiched between the Dharwar Craton in the north and the Neoarchean–Proterozoic crustal blocks to the south, the Coorg Block in southern India is composed dominantly of a suite of arc magmatic rocks including charnockites, TTG (tonalite–trondhjemite–granodiorite)-related granitoid suite and felsic volcanic tuffs together with minor accreted oceanic remnants along the periphery of the block. Coeval mafic and felsic magmatism with magma mixing and mingling in an arc setting is well represented in the block. Here we present the petrology, geochemistry, zircon U–Pb geochronology and Lu–Hf isotopes of all the major lithologies from this block. Computation of metamorphic P–T conditions from mineral chemical data shows consistent granulite-facies P–T conditions of 820–870°C and up to 6kbar. Our geochemical data from major, trace and REE on representative samples of the dominant rock types from the Coorg Block corroborate an arc-related signature, with magma generation in a convergent margin setting. The zircon data yield weighted mean 207Pb/206Pb ages of 3153.4±9 to 3184.0±5.5Ma for syenogranites, 3170.3±6.8Ma for biotite granite, 3275±5.1Ma for trondhjemite, 3133±12 to 3163.8 ±6.9Ma for charnockites, 3156±10 to 3158.3±8.2 for mafic enclaves, 3161±16Ma for diorite and 3173±16Ma for felsic volcanic tuff. An upper intercept age of 3363±59Ma and a lower intercept age of 2896±130Ma on zircons from a charnockite, as well as an evaluation of the Th/U values of the zircon domains against respective 207Pb/206Pb ages suggest that the Mesoarchean magma emplacement which probably ranged from >3.3 to 3.1Ga was immediately followed by metamorphism at ca. 3.0 to 2.9Ga. The ages of magmatic zircons from the charnockites and their mafic granulite enclaves, as well as those from the volcanic tuff and biotite granite, are all remarkably consistent and concordant marking ca. 3.1Ga as the peak of subduction-related crust building in this block, within the tectonic milieu of an active convergent margin. The majority of zircons from the Coorg rocks show Hf isotope features typical of crystallization from magmas derived from juvenile sources. Their Hf crustal model ages suggest that the crust building might have also involved partial recycling of basement rocks as old as ca. 3.8Ga. The crustal blocks in the Southern Granulite Terrane in India preserve strong imprints of major tectonothermal events at 2.5Ga, 2.0Ga, 0.8Ga and 0.55Ga associated with various subduction–accretion–collision or rifting events. However, the Coorg Block is exceptional with our data suggesting that none of the above events affected this block. Importantly, there is also no record in the Coorg Block for the 2.5Ga pervasive regional metamorphism that affected all the other blocks in this region. The geochronological data raise the intriguing possibility that this block is an exotic entity within the dominantly Neoarchean collage in the northern domain of the Southern Granulite Terrane of India. The Mesoarchean arc-related rocks in the Coorg Block suggest that the magma factories and their tectonic architecture in the Early Earth were not markedly different from those associated with the modern-style plate tectonics.

Atomic and molecular structures of positronium, dipositronium and positronium hydride

AbstractThe three positron based chemical entities, analogous to hydrogen atom, hydrogen molecule and hydride, are drawing increasing attention in the literature. While a lot is known about the binding energies, not much is known about the radii of the atoms and ions and bond lengths and structures of these exotic entities. This article brings for the first time exact values of these structural properties which are comparable with known data. It is hoped that the results will be of help for a better understanding and further development of the chemistry and physics of these exotic compounds and of their possible role as intermediates in chemical and interfacial processes.

Fictionalism and inferential safety

Many of us find ‘Spartan’ ontologies attractive. Spartans reject the exotic entities countenanced by their rivals; they find barren landscapes appealing and pour scorn upon those who countenance numbers, composite objects and possibilia. But Spartan life is not easy. Common sense tells us that big things have smaller parts and that there are two prime numbers between four and eight. Spartans seem destined to clash with what we ordinarily think and say. Spartan ontologies, then, are attractive only if the Spartan can ‘reconstruct’ the world of common sense and science. There are a variety of ways to understand what ‘reconstruction’ amounts to, but a historically popular option was to attempt to provide non-committal paraphrases of the ontologically problematic sentences. The problem is that the paraphraser is often troubled by the complexity found in ordinary talk. (See, e.g., the problems which Uzquiano (2004) finds with the suggestion that ordinary talk of composite objects can be paraphrased by talk of arrangements of simple objects.) But if paraphrasis cannot secure the material adequacy of ontologically radical views, what can?

ANALYTICAL CONSIDERATIONS ABOUT THE COSMOLOGICAL CONSTANT AND DARK ENERGY

The accelerated expansion of the universe has now been confirmed by several independent observations including those of high redshift type Ia supernovae, and the cosmic microwave background combined with the large scale structure of the universe. Another way of presenting this kinematic property of the universe is to postulate the existence of a new and exotic entity, with negative pressure, the dark energy (DE). In spite of observationally well established, no single theoretical model provides an entirely compelling framework within which cosmic acceleration or DE can be understood. At present all existing observational data are in agreement with the simplest possibility that the cosmological constant be a candidate for DE. This case is internally self-consistent and noncontradictory. The extreme smallness of the cosmological constant expressed in either Planck, or even atomic units means only that its origin is not related to strong, electromagnetic, and weak interactions. Although in this case DE reduces to only a single fundamental constant we still have no derivation from any underlying quantum field theory for its small value. From the principles of quantum cosmologies, for example, it is possible to obtain the reason for an inverse-square law for the cosmological constant with no conflict with observations. Despite the fact that this general expression is well known, in this work we introduce families of analytical solutions for the scale factor different from the current literature. The knowledge of the scale factor behavior might shed some light on these questions mentioned above since the entire evolution of a homogeneous isotropic universe is contained in the scale factor. We use different parameters for these solutions and with these parameters we establish a connection with the equation of state for different DE scenarios.

Debate about science and religion continues

The issues of scientific validity and science versus pseudoscience were never addressed in any courses I took as an undergraduate science major, and I observe the same situation in today’s university introductory science courses. How are undergraduates—or graduate students, for that matter—supposed to learn these things? Murray Peshkin is correct when he says, “We need to do better.”For about the past five years, I have begun my introductory astronomy courses with a detailed interactive talk on the nature of science and critical thinking. I incorporate a study of logical fallacies, another item missing from most science courses. I use actual letters to the editor of the local newspaper as debunking fodder. This introduction to critical thinking takes about two weeks, but by the end of the semester, my students know how to tell science from pseudoscience and belief, and they know how to gauge the scientific validity of a claim. Instructors who leave this material out of their courses are doing a great injustice to students and to science in general. The presentation I use in my classes is available on my website http://www.sticksandshadows.com) along with a small but growing collection of custom applications of critical thinking to astronomy.All introductory science courses should be built around critical thinking, with examples from the various scientific disciplines providing applications. If students never understand the nature of science, they will never truly understand how and why we know about exotic entities like black holes. My experience has been that students welcome discussion on the differences between science and religion, a necessary topic when it comes to critical thinking. In a recent semester, three students told me they were planning to become ministers, and they appreciated the opportunity to develop critical-thinking skills. One of these students told me that elders in his church warned him to avoid science classes because they would be a waste of time and would not help him become a better minister. How much clearer does the need have to be before we do something about it?© 2007 American Institute of Physics.

Microbe: Are We Ready for the Next Plague?

Microbe: Are We Ready for the Next Plague? by Alan Zelicoff and Michael Bellomo is a comprehensive, yet succinct, account of the threat to public health posed by microbial pathogens. What distinguishes this book from the surfeit of recent books hyping the threat of bioterrorism are its balanced perspective and elucidation of naturally emerging disease threats, such as severe acute respiratory syndrome (SARS) or West Nile virus, as exotic entities requiring a rapid and effective response; Mother Nature is quite the bioterrorist herself. Early recognition that an event has occurred is key to containment of the nascent epidemic. The authors provide sufficient basic science background to bring the uninitiated up to speed on a variety of exotic and recently introduced microbes in engagingly titled chapters such as Birds that Fell from the Sky (West Nile), Corona of Death (SARS), and Something in the Water (Cryptosporidium). In addition, they describe hantavirus pulmonary syndrome, mad cow disease, and Legionnaires' disease in the context of recent public health emergencies. The authors also explain why both smallpox and anthrax are more than abstract concerns as agents of bioterrorism, on the basis of weaponization history, intrinsic attributes, and realistic scenarios. An account of the 1970 smallpox outbreak, which occurred in Aralsk, Kazakhstan, as a consequence of open air testing of a smallpox weapon by the Soviets is an eye-opener; there should be no doubts about capability and intent after reading this story. The scenarios are well chosen and informative; they highlight the importance of early recognition that something has happened and breaking the disease cycle close to the index case. The unifying theme of the book is the importance of syndrome-based surveillance in achieving this goal. The authors dismiss BIOWATCH (air-monitoring devices to detect and identify microbes in aerosol clouds) as a well-intended but expensive work in progress, to put it charitably. BIOSENSE is a national surveillance system that they say has not been implemented in any substantive way. I reluctantly find myself in agreement with these assessments and receptive to their suggestions to implement an emerging diseases reporting system based on syndromic reporting. Healthcare providers recognize syndromes, not microbial diseases. How long did it take to recognize monkeypox in 2003? The hantavirus associated with lethal pulmonary syndrome in New Mexico in 1993 was recognized only when the pattern emerged among previously healthy young adults living in rustic conditions on a Navajo reservation. The authors describe a product they dub Syndromic Reporting Information System (SYRIS) as a beta test product that has been deployed on a limited, regional basis and promises to provide a near instantaneous map of syndromic reports and to comply with all Centers for Disease Control and Prevention requirements for electronic reporting systems. Like most good ideas, simplicity is central to the SYRIS concept; it is likely to succeed because participating doctors, nurses, and veterinarians (most of the exotic pathogens are zoonoses) can report syndromic occurrences in 15 seconds or less and will be rewarded with instantaneous feedback and tailored reports and alarms. While this section does read a bit like an infomercial, the concept is sound and worthy of serious consideration by public health officials and policy makers. This book is the best of its genre and is recommended for anyone interested in understanding and managing the risks associated with emerging microbial threats.

On "Alexander's" Dictum

The dictum “To exist is to have causal powers” is discussed sympathetically by Plato in The Sophist 246E‐248A. The question what this slogan means in Plato’s language, is a challenge for a scholar. To ask what it means in our common language risks raising a complex question. The idea of causal power is of folk origin and is deeply connected with the idea of agency. It is not the sledgehammer that causes the rock to crumble, but John Henry or his rival, the steam drill. The intrusion of agency can be reduced by shifting the focus from “causal power” to “causal role”, but this further clouds an already vague criterion. As an ontological criterion, the requirement of causal power has been primarily invoked in modern times, by materialists. This tends to proceed from the assumption that standard material objects pass easily. This is unwarranted for more than one reason. When we try to imagine examples of causal power, three competing metaphysical theories differ over the initial candidates. Many dualists and materialists may agree (hastily, it will be argued later) that material objects unproblematically have causal powers, just by virtue of having mass. Exotic entities of microphysics may pose problems, but these include problems for the very meaning of the classification of “material” or “physical”. Or consider the space in my office. Many would incline to the view that in this space there are points, lines, circles, triangles, etc. They would agree that there is in my office more than one rectangle with area greater than 200 square feet, but no circle with area that large. They would agree that there are as many points in the space in my office as there are in Grand Central Station, etc. These would be points of physical space and physical points of space (why not?). But they have no mass and assigning them causal powers would call for a different approach from the one followed for massive things. Just how it would be made out is not

Three Roads to Quantum Gravity

The Holy Grail of modern physics is a theory of the universe that unites two seemingly opposing pillars of modern science: Einstein's theory of general relativity, which deals with large-scale phenomena (planets, solar systems and galaxies), and quantum theory, which deals with the world of the very small (molecules, atoms, electrons). In Three Roads to Quantum Gravity, Lee Smolin provides the first concise and accessible overview of current attempts to reconcile these two theories in a final "theory of everything. " This is the closest anyone has ever come to devising a completely new theory of space, time and the universe to replace the Newtonian ideas that were the foundation of all science until the beginning of the twentieth century. Lee Smolin, who has spent his career at the forefront of these new discoveries, presents for the first time the main ideas behind the new developments that have brought a quantum theory of gravity in sight. He explains in simple terms what scientists are talking about when they say the world is made from exotic entities such as loops, strings, and black holes. As he does so, he tells the fascinating stories behind these discoveries: the rivalries, epiphanies, and intrigues he witnessed firsthand. Science Masters Series

Adiabatic pulses.

Adiabatic pulses are sometimes considered to be mysterious and exotic entities which are difficult to understand, complex to generate and impractical to implement. This work is an attempt to bring familiarity and to fulfill the preliminary needs of anyone interested in learning more about this subject. The response of magnetization to stimuli produced by adiabatic pulses is analyzed using vector representations in a frequency modulated rotating frame. The first section deals with basic principles of amplitude and frequency modulated pulses and a vector representation in a second rotating frame is used to explain how the adiabatic condition can be satisfied. The subsequent section explains the principles of offset independent adiabaticity. These principles are then used to design optimal functions for the amplitude, frequency, and magnetic field gradient modulations for adiabatic inversion pulses. The last section considers some practical aspects for those who want to develop methodologies involving adiabatic pulses.

Arabic Literature and the Nobel Prize

By ROGER ALLEN For many centuries the Arabs have constituted for the Western world an alien and often confrontational entity, a quintessential other. The posture can be traced back at least to the Crusades, and as we know to our cost from current conflicts in Ireland, Lebanon, and the Gulf, wars based on religious belief are particularly capable of engendering misinformation and misunderstandings of prolonged duration. In spite of recent developments in what is known both about the Arab world and also about the processes by which that knowledge is interpreted, many Western attitudes of considerable antiquity still persist. The was so designated by the Western imperialist interests of previous generations (to which the Middle East was middle), and the inhabitants of the region seem to have been condemned by their very proximity to Europe, and therefrom by the frequency of military confrontations with the European political powers throughout the ages, to be the subject of a wide variety of religious and cultural polemics. By contrast, the nations of what was simultaneously designated as the Far were a more remote and exotic entity, something which, within a less directly confrontational context, seems to have promoted among Western scholars (perhaps automatically) a closer attention to the literary production of the region. More recently, events such as the series of conflicts following 'the foundation of the State of Israel and the emergence of a newly invigorated fundamentalist Islam have given the Western nations their share of anxiety and often annoyance. However, rather than being seen as offering opportunities for a renewed interest in the history and nature of Arabo-Islamic culture, these contemporary confrontations and conflicts have tended to cement still further attitudes which lead to a widespread unfamiliarity with this elaborate complex of nations and peoples and a concomitant reluctance to change the situation.

Histidinemia

Time was when histidinemia was considered a rare, exotic entity, relegated to specialists and academic researchers. However, there are mounting reasons for revising this attitude. For one thing, we now realize that this inborn error of metabolism is hardly rare. An incidence of one in 14,000 has been reported in the United States,1and studies in other parts of the world have shown rates ranging from one in 11,0002to one in 17,000.3In the article on histidinemia published in this issue (see p 227), Ito and co-workers note that in Japan one person in 10,000 may be histidinemic. In the United States, screening for histidinemia is now mandatory in at least one state (New York). Moreover, the implications of this law for physicians at large clearly transcend state boundaries, and it behooves all American physicians to be aware of this condition. To what extent dietary management