Multimetric extension of the PPN formalism: experimental consistency of repulsive gravity

Recently we discussed a multimetric gravity theory containing several copies of standard model matter each of which couples to its own metric tensor. This construction contained dark matter sectors interacting repulsively with the visible matter sector, and was shown to lead to cosmological late-time acceleration. In order to test the theory with high-precision experiments within the solar system we here construct a simple extension of the parametrized post-Newtonian (PPN) formalism for multimetric gravitational backgrounds. We show that a simplified version of this extended formalism allows the computation of a subset of the PPN parameters from the linearized field equations. Applying the simplified formalism we find that the PPN parameters of our theory do not agree with the observed values, but we are able to improve the theory so that it becomes consistent with experiments of post-Newtonian gravity and still features its promising cosmological properties.Comment: 19 pages, no figures, journal versio

70 years later – New research at Holley Shelter, a Middle and Later Stone Age site in KwaZulu-Natal, South Africa

In 1952, Gordon Cramb published the first report on his excavations at Holley Shelter, in KwaZulu-Natal, South Africa. Although Cramb’s work implied organic preservation associated with a unique stone tool assemblage from a Middle Stone Age (MSA) context, Holley Shelter disappeared from the archaeological landscape until 2015, when we provided a reinvestigation of the lithic assemblages from the 1950s. Our study indicated a tentative chronological framework around Marine Isotope Stage 3 (MIS3) for the human occupation of the site. However, Cramb’s excavations did not produce reliable chronometric ages and the botanical and zoological finds from Holley Shelter remain for the most part unstudied. This is problematic as the site constitutes one of the few inland MSA rock shelters of KwaZulu-Natal featuring organic preservation. In 2022, 70 years after Cramb’s first report, we started a new research project focusing on renewed excavations to obtain archaeological remains from a controlled stratigraphy, absolute chronometric ages and reliable data on the palaeoenvironment at the border between the coastal belt and the midlands of KwaZulu-Natal. Here, we provide initial results from the first field campaign in 2022 on the stratigraphic sequence and archaeological finds and discuss their implications for future multidisciplinary research. Significance: Environmental change can have a strong impact on hunter-gatherer behaviour, migration and technological choices. It is thus crucial to contextualise archaeological material with a strong palaeoenvironmental record. The inland of KwaZulu-Natal, South Africa, represents an understudied region in terms of Stone Age archaeological sites and palaeoenvironmental record. Holley Shelter is one of the few sites in South Africa with excellent organic preservation and a deep stratigraphic record, which provide a great opportunity to investigate human-landscape interaction and technological change throughout the Middle and Later Stone Age

Spatial and temporal variation of body size among early Homo.

The estimation of body size among the earliest members of the genus Homo (2.4-1.5Myr [millions of years ago]) is central to interpretations of their biology. It is widely accepted that Homo ergaster possessed increased body size compared with Homo habilis and Homo rudolfensis, and that this may have been a factor involved with the dispersal of Homo out of Africa. The study of taxonomic differences in body size, however, is problematic. Postcranial remains are rarely associated with craniodental fossils, and taxonomic attributions frequently rest upon the size of skeletal elements. Previous body size estimates have been based upon well-preserved specimens with a more reliable species assessment. Since these samples are small (n < 5) and disparate in space and time, little is known about geographical and chronological variation in body size within early Homo. We investigate temporal and spatial variation in body size among fossils of early Homo using a 'taxon-free' approach, considering evidence for size variation from isolated and fragmentary postcranial remains (n = 39). To render the size of disparate fossil elements comparable, we derived new regression equations for common parameters of body size from a globally representative sample of hunter-gatherers and applied them to available postcranial measurements from the fossils. The results demonstrate chronological and spatial variation but no simple temporal or geographical trends for the evolution of body size among early Homo. Pronounced body size increases within Africa take place only after hominin populations were established at Dmanisi, suggesting that migrations into Eurasia were not contingent on larger body sizes. The primary evidence for these marked changes among early Homo is based upon material from Koobi Fora after 1.7Myr, indicating regional size variation. The significant body size differences between specimens from Koobi Fora and Olduvai support the cranial evidence for at least two co-existing morphotypes in the Early Pleistocene of eastern Africa.JTS would also like to acknowledge generous funding from the Natural Environment Research Council, UK, (Grant Number: NE/M/S/2003/00069) for supporting this research.This is the final published version. It first appeared at http://www.sciencedirect.com/science/article/pii/S0047248415000287#

No-go theorem for bimetric gravity with positive and negative mass

We argue that the most conservative geometric extension of Einstein gravity describing both positive and negative mass sources and observers is bimetric gravity and contains two copies of standard model matter which interact only gravitationally. Matter fields related to one of the metrics then appear dark from the point of view of an observer defined by the other metric, and so may provide a potential explanation for the dark universe. In this framework we consider the most general form of linearized field equations compatible with physically and mathematically well-motivated assumptions. Using gauge-invariant linear perturbation theory, we prove a no-go theorem ruling out all bimetric gravity theories that, in the Newtonian limit, lead to precisely opposite forces on positive and negative test masses.Comment: 19 pages, no figures, journal versio

Implications of Nubian-like core reduction systems in southern Africa for the identification of early modern human dispersals

Lithic technologies have been used to trace dispersals of early human populations within and beyond Africa. Convergence in lithic systems has the potential to confound such interpretations, implying connections between unrelated groups. Due to their reductive nature, stone artefacts are unusually prone to this chance appearance of similar forms in unrelated populations. Here we present data from the South African Middle Stone Age sites Uitpanskraal 7 and Mertenhof suggesting that Nubian core reduction systems associated with Late Pleistocene populations in North Africa and potentially with early human migrations out of Africa in MIS 5 also occur in southern Africa during early MIS 3 and with no clear connection to the North African occurrence. The timing and spatial distribution of their appearance in southern and northern Africa implies technological convergence, rather than diffusion or dispersal. While lithic technologies can be a critical guide to human population flux, their utility in tracing early human dispersals at large spatial and temporal scales with stone artefact types remains questionable

Propagation of gravitational waves in multimetric gravity

We discuss the propagation of gravitational waves in a recently discussed class of theories containing N >= 2 metric tensors and a corresponding number of standard model copies. Using the formalism of gauge-invariant linear perturbation theory we show that all gravitational waves propagate at the speed of light. We then employ the Newman-Penrose formalism to show that two to six polarizations of gravitational waves may exist, depending on the parameters entering the equations of motion. This corresponds to E(2) representations N_2, N_3, III_5 and II_6. We finally apply our general discussion to a recently presented concrete multimetric gravity model and show that it is of class N_2, i.e., it allows only two tensor polarizations, as it is the case for general relativity. Our results provide the theoretical background for tests of multimetric gravity theories using the upcoming gravitational wave experiments.Comment: 21 pages, no figures, journal versio

Lithic technology and behavioral variability during the Middle Stone Age of southern Africa: Implications for the evolution and dispersal of early modern humans

The Middle Stone Age (MSA) of Africa encompasses the archaeological background for the origin, early evolution and global dispersal of Homo sapiens. This dissertation project used behavioral information attained from the analysis of MSA stone artifacts, in concert with additional archaeological data and new theoretical concepts, to assess research questions pertaining to key issues in current MSA archaeology and human evolution: What is the nature of coastal adaptations during the MSA and how did they affect the evolution and dispersal of Homo sapiens? Did modern humans in southern Africa possess a less complex behavioral repertoire and inferior cultural abilities before and after the Still Bay (SB) and Howiesons Poort (HP) as suggested by the influential “Synthetic Model”? To what extent can analyses of stone tools from the late MSA inform early migrations of Homo sapiens out of Africa? Lithic assemblages from six southern African MSA sites, dating to MIS 5 and MIS 3, provide the principle empirical basis to answer these questions. Concerning the first research topic, based on analyses on the site (Hoedjiespunt 1), regional (sub-Saharan Africa) and continental levels (Africa), the findings of this dissertation demonstrate the systematic, stable and long-term character of MSA coastal adaptations by at least MIS 5e. These behavioral adaptations had ample potential to affect the biological and cultural evolution of Homo sapiens. The ability to thrive in variable coastal ecosystems, and a general increase in behavior flexibility, constituted necessary prerequisites to disperse out of Africa along a mainly coastal route in a rapid and successful manner after ~130 ka. Lithic analyses at the main study site of Sibudu revealed the presence of distinctive, sophisticated and structured stone artifact assemblages during MIS 3 which are used to refine the concept of the “Sibudan” as a new cultural-taxonomic unit of the MSA. Comparative analyses suggest increased regionalization of lithic technology in southern Africa during MIS 3, the maintenance of advanced lithic technology and complex cultural repertoires, as well as dense populations in some areas. These findings reject the dominant Synthetic Model by showing that complex behaviors were well-established in human populations before and after the HP and SB. The results also falsify ideas of cultural regression and demographic collapses after the HP. Regarding the third major topic, the thesis shows how the phenomenon of convergence can confound the common approach by Paleolithic archaeologists to track large-scale dispersals of modern humans out of Africa by means of stone artifacts. The demonstration of an independent innovation of “Nubian” core technology during MIS 3 in southern Africa, with these artifact types having recently been used to monitor the earliest migrations of modern humans from north-eastern Africa to Arabia, provides a cautionary example that single core or tool types cannot adequately trace such dispersals on large temporal and spatial scales. Apart from providing new insights into the evolution and dispersal of modern humans, the thesis highlights the need for novel approaches in lithic analyses and a holistic bio-cultural perspective on human evolution

O processo da decisão curricular no ensino de graduação em administração relacionado com as novas exigências da educação superior

Este trabalho foi desenvolvido com base em uma análise das Diretrizes Curriculares Nacionais (DCN) da República Federativa do Brasil, no que diz respeito ao curso de graduação em Administração, para inferir sobre os elementos que orientam a decisão curricular no contexto da organização desse curso. O estudo é fruto da investigação realizada na Universidade do Minho, no nível de doutoramento em Ciências da Educação na especialidade: Desenvolvimento Curricular do Instituto de Educação. Através da Resolução no 4 da Câmara de Educação Superior (CES) e do Conselho Nacional de Educação (CNE) - dispositivo legal-, as DCN orientam a organização do curso de Administração. A aplicabilidade é um dos requisitos para as instituições de ensino superior (IES) permanecerem legalizadas no MEC. Historicamente, as universidades públicas têm assumido uma postura de reflexão, criação, crítica, democratização do saber, ao mesmo tempo que se têm preocupado com a eficiência e a eficácia no uso dos recursos e procedimentos para alcançar as metas previstas (Moreira, 2005). Em contrapartida, a proposta nacional para as IES traz alguns elementos de reflexão para a organização dos projetos curriculares, criando uma base comum entre as IES, em um período histórico em que os Estados Nacionais procuram atender às novas exigências da nova ordem mundial do mundo globalizado. As novas exigências de formação, na sociedade da informação e do conhecimento (Morgado), têm orientado o caminho que os cursos universitários devem trilhar e, no âmbito da decisão curricular (Pacheco, 2009), os elementos norteadores trazem implícitos uma política de gestão do ensino e da formação profissional. A metodologia se constitui em uma análise documental, com a apreciação e o processo de inferência sobre as DCN do curso de graduação em Administração. Essa investigação inicial é importante no que diz respeito à análise de elementos que estão implícitos na ideia da democratização do ensino superior no Brasil, visto que é a partir da elaboração do projeto pedagógico dos cursos, entre os quais o de Administração, respeitando as orientações das DCN e relacionando quantidade e qualidade, que as IES conseguem verbas públicas para implementar suas ações na área planejada. Essa produção inicial é parte de uma reflexão mais aprofundada sobre o processo de decisão curricular em uma universidade pública brasileira

Curriculum and curricular management: an initial reflection

Este trabalho tem como objetivo fazer uma reflexão inicial sobre o projeto pedagógico do curso de Administração da Universidade Federal do Tocantins UFT). É parte de uma pesquisa realizada em Ciências da Educação, especialidade de Desenvolvimento Curricular do Instituto de Educação da Universidade do Minho (Portugal), no nível de doutorado. O procedimento adotado é uma análise documental e qualitativa da Resolução do Conselho Nacional de Educação e da Câmara de Ensino Superior (CNE/CES) nº 4/2005‐que trata das Diretrizes Curriculares Nacionais do Curso de Graduação em Administração (bacharelado)  ‐ e também do projeto pedagógico do curso de Administração da UFT. Concluiu‐se que esse movimento da universidade de planejar o currículo,    na busca de superar a fragmentação do conhecimento promovido pela lógica da estrutura disciplinar, ainda está em processo de discussão inicial, imprescindível no mundo globalizado, e que os professores do curso de Administração da UFT encontram se no nível de construção de um novo modo de gerenciar a prática curricularThis work aims at developing an initial reflection on the pedagogical project of the Business Administration course at Tocantins’s Federal University (UFT). It is part of research conducted in a doctoral level course on Education at the Institute of Education, University of Minho, in Portugal, in the field of curriculum development. The procedure adopted was a qualitative and documental analysis of the National Education Council and Board of Higher Education Resolution (CNE/CES) nº 4/2005, Brazil, which deals with the National Curricular Guidelines for Undergraduate courses in Business Administration, and also an analysis of the pedagogical project of the Business Administration course at UFT. We came to the conclusion that the university movement of planning the curriculum, in search of overcoming the fragmentation of knowledge promoted by the logic of a disciplinary structure, is still in an initial discussion process, which is essential in a globalized world. In this way, teachers of UFT’s Business Administration course are just starting the design of a new way of managing curriculum practice