Hasil untuk "History of Spain"

Mikhail G. Katz

Infinitesimals have seen ups and downs in their tumultuous history. In the 18th century, d'Alembert set the tone by describing infinitesimals as chimeras. Some adversaries of infinitesimals, including Moigno and Connes, picked up on the term. We highlight the work of Cauchy, Noël, Poisson and Riemann. We also chronicle reactions by Moigno, Lamarle and Cantor, and signal the start of a revival with Peano.

Kiwhan Song, Boyuan Chen, Max Simchowitz et al.

Classifier-free guidance (CFG) is a key technique for improving conditional generation in diffusion models, enabling more accurate control while enhancing sample quality. It is natural to extend this technique to video diffusion, which generates video conditioned on a variable number of context frames, collectively referred to as history. However, we find two key challenges to guiding with variable-length history: architectures that only support fixed-size conditioning, and the empirical observation that CFG-style history dropout performs poorly. To address this, we propose the Diffusion Forcing Transformer (DFoT), a video diffusion architecture and theoretically grounded training objective that jointly enable conditioning on a flexible number of history frames. We then introduce History Guidance, a family of guidance methods uniquely enabled by DFoT. We show that its simplest form, vanilla history guidance, already significantly improves video generation quality and temporal consistency. A more advanced method, history guidance across time and frequency further enhances motion dynamics, enables compositional generalization to out-of-distribution history, and can stably roll out extremely long videos. Project website: https://boyuan.space/history-guidance

Antón M. Pazos

Robert van Leeuwen

The early history of string theory is marked by a shift from strong interaction physics to quantum gravity. The first string models and associated theoretical framework were formulated in the late 1960s and early 1970s in the context of the S-matrix program for the strong interactions. In the mid-1970s, the models were reinterpreted as a potential theory unifying the four fundamental forces. This paper provides a historical analysis of how string theory was developed out of S-matrix physics, aiming to clarify how modern string theory, as a theory detached from experimental data, grew out of an S-matrix program that was strongly dependent upon observable quantities. Surprisingly, the theoretical practice of physicists already turned away from experiment before string theory was recast as a potential unified quantum gravity theory. With the formulation of dual resonance models (the "hadronic string theory"), physicists were able to determine almost all of the models' parameters on the basis of theoretical reasoning. It was this commitment to "non-arbitrariness", i.e., a lack of free parameters in the theory, that initially drove string theorists away from experimental input, and not the practical inaccessibility of experimental data in the context of quantum gravity physics. This is an important observation when assessing the role of experimental data in string theory.

Leonid I. Gurvits

Space Very Long Baseline Interferometry is a radio astronomy technique distinguished by a record-high angular resolution reaching single-digit microseconds of arc. The paper provides a brief account of the history of developments of this technique over the period 1960s-2020s.

Doreen Fraser, Maria Papageorgiou

The formulation of a measurement theory for relativistic quantum field theory (QFT) has recently been an active area of research. In contrast to the asymptotic measurement framework that was enshrined in QED, the new proposals aim to supply a measurement framework for measurements in local spacetime regions. This paper surveys episodes in the history of quantum theory that contemporary researchers have identified as precursors to their own work and discusses how they laid the groundwork for current approaches to local measurement theory for QFT.

Clara Medina-García, Clara Medina-García, Sharmada Nagarajan et al.

Literatures on social innovation, collective agency and multi-actor collaboration stress the importance of action research and joint problematization to research ongoing processes of collaboration and transformation to advance both theory and practice in these fields. In this paper we analyze our experience building a transdisciplinary action research (TAR) trajectory between 2020 and 2021 to investigate socially innovative multi-actor collaborations (IMACs) and urban governance innovation trajectories in the city of Leuven (Belgium). We specifically focus on (1) how we involved a wide array of researchers, stakeholders and practitioners in the TAR trajectory; (2) how we enacted joint problematization and action, ensuring that all facilitative leadership roles were taken care of; (3) the challenges that the specific COVID context posed on TAR and the innovative tools and approaches we took to adapt under such circumstances; and (4) how our TAR contributed to the ongoing IMACs in Leuven. Discussing our experience in relation to issues raised in action research literature, we summarize key dimensions, roles and tasks necessary in TAR to enable facilitative leadership and multi-actor collaboration and successfully drive joint problematization and transformative change. We conclude that our TAR trajectory in Leuven became a case study of IMAC in itself, and so learnings from our TAR directly dialogue with and inform our empirical analysis of the performance of IMACs too. Through this realization and the analysis of our experience, we get to broader question the role of action research and researchers in urban governance innovation.

Gustavo Rodrigues Rocha, Dean Rickles, Florian J. Boge

It will be presented in this chapter a historical account of the consistent histories interpretation of quantum mechanics based on primary and secondary literature. Firstly, the formalism of the consistent histories approach will be outlined. Secondly, the works by Robert Griffiths and Roland Omnès will be discussed. Griffiths' seminal 1984 paper, the first physicist to have proposed a consistent-histories interpretation of quantum mechanics, followed by Omnès' 1990 paper, were instrumental to the consistent-histories model based on Boolean logic. Thirdly, Murray Gell-Mann and James Hartle's steps to their own version of consistent-histories approach, motivated by a cosmological perspective, will then be described and evaluated. Gell-Mann and Hartle understood that spontaneous decoherence could path the way to a concrete physical model to Griffiths' consistent histories. Moreover, the collective biography of these figures will be put in the context of the role played by the Santa Fe Institute, co-founded by Gell-Mann in 1984 in Santa Fe, New Mexico, where Hartle is also a member of the external faculty.

Leonardo Castellani

A formalism is proposed to describe entangled quantum histories, and their entanglement entropy. We define a history vector, living in a tensor space with basis elements corresponding to the allowed histories, i.e. histories with nonvanishing amplitudes. The amplitudes are the components of the history vector, and contain the dynamical information. Probabilities of measurement sequences, and resulting collapse, are given by generalized Born rules: they are all expressed by means of projections and scalar products involving the history vector. Entangled history states are introduced, and a history density matrix is defined in terms of ensembles of history vectors. The corresponding history entropies (and history entanglement entropies for composite systems) are explicitly computed in two examples taken from quantum computation circuits.

Carl-Fredrik Nyberg-Brodda

This article aims to be a self-contained account of the history of the B. B. Newman Spelling Theorem, including the historical context in which it arose. First, an account of B. B. Newman and how he came to prove his Spelling Theorem is given, together with a description of the author's efforts to track this information down. Following this, a high-level description of combinatorial group theory is given. This is then tied in with a description of the history of the word problem, a fundamental problem in the area. After a description of some of the theory of one-relator groups, an important part of combinatorial group theory, the natural division line into the torsion and torsion-free case for such groups is described. This culminates in a statement of and general discussion about the B. B. Newman Spelling Theorem and its importance.

Fernando B. Figueiredo, João M. Fernandes

In 1782 José Monteiro da Rocha, astronomer and professor of the University of Coimbra, presented in a public session of the Royal Academy of Sciences of Lisbon a memoir on the problem of the determination of the comets' orbits. Only in 1799, the "Determinação das Orbitas dos Cometas" (Determination of the orbits of comets) would be published in the Academy's memoires. In that work, Monteiro da Rocha presents a method for solving the problem of the determination of the parabolic orbit of a comet from three observations. Monteiro da Rocha's method is essentially the same method proposed by Olbers and published under von Zach's sponsorship two years before, in 1797. To have been written and published in Portuguese was certainly a hindrance for its dissemination among the international astronomical community. In this article, we intend to present Monteiro da Rocha's method and trying to see to what extent Gomes Teixeira's assertion (Teixeira 1934) that Monteiro da Rocha and Olbers must figure together in the history of astronomy, as the first inventors of a practical and easy method for the determination of parabolic orbits of comets, is justified.

Roberto Sánchez-Cabrero, Óscar Costa-Román, Francisco Javier Pericacho-Gómez et al.

This study describes the social and demographic profile of the first generation of users of marketed virtual reality (VR) viewers in Spain and, subsequently, it assesses the interest in its use as a learning tool. For that purpose, an online questionnaire created ad hoc was administered to a sample of 117 participants. The relationship between twelve variables was analysed comparing means through the Snedecor's F distribution and the contingency tables through the Chi-squared test and Somers' D. Among other issues, it was concluded that the virtual reality user profile at present corresponds to a person older than 36, mainly men, with higher education and having acquired their viewer no longer than one year ago. Concerning the interests of virtual reality users as a learning tool, only a few of them currently use virtual reality for this aim, but they mainly show an interest in using the virtual reality as a learning method and they feel optimism regarding the future use of this technology as a learning tool. However, this is not the case among users of video game consoles (PSVR), who are mainly men not interested in their use as a learning tool at present. Finally, it can be stated that current use as a learning tool among teachers and students is occasional and preferably via smartphones.

Pierre Pretou

The reception and appropriation of Roman history under the Valois through copies and translations of luxurious manuscripts owned by these kings, their relatives and great officers, connect the medieval imaginary of antiquity to this dynasty. French political iconography of the 14th and 15th centuries combines the governance of the City of Rome with the origins of the kingdom since the translation of Ab Urbe Condita of Tite-Live by Pierre Bersuire, the copies of Jean Mansel's Fleurs des histoires, the translations of De Civitate Dei by Raoul de Presles and the vernacular translation of the writings of Valère Maxime by Simon de Hesdin and Nicolas de Gonesse. By thousands, these miniatures on a universe of men and cities, order and disorder, peace and revenge, concord and discord, identify the public space, the speech, the just power, the contestation, the tyranny, the circulation pacificator of the law, but rarely give way to women, except to associate them with bloody scenes. The serial analysis of the narrow corpus of female representation shows that the appropriation of the image of Roman history gives a singular place to the genre in the representation of conflicts and their resolution in urban areas. The painted women who emerge from Roman stories of the late Middle Ages French escort a world of ancient men experiencing the soothing role of law. Can we conclude for these rare women who accompany scenes of conflict and peace that the painter gives them a historical role as mediators and reinterprets the actions of Roman women? Does he reconsider the construction of public order at the end of the French Middle Ages or is it first of all the historized formulation of a political theory of marriage?

Ian Crawford

Astrobiology is the field of science devoted to searching for life elsewhere in the Universe. It is inherently interdisciplinary, integrating results from multiple fields of science, and in this respect has strong synergies with 'big history'. I argue that big history and astrobiology are both acting to widen human perspectives in intellectually and socially beneficial directions, especially by enhancing public awareness of cosmic and evolutionary worldviews. I will further argue that these perspectives have important implications for the social and political organisation of humanity, including the eventual political unification of our planet. Astrobiology and big history are also concerned with the future of humanity, and I will argue that this future will be culturally and intellectually enriched if it includes the exploration of the universe around us.

Zhixin Wang

This short essay traces the conceptual history of micro- and macroscopicity in the context of physical science. By focusing on three distinct episodes spanning five centuries, we show the scientific and philosophical meanings of this antonym pair, despite never being far from "the small" and "the large," have been evolving as the frontier of science advances. We analyze the intellectual and material impetus for these movements, and conclude that this conceptual history reflects the changing interaction between the natural world and humankind.

Sánchez Llanes, Iván

En el Barroco hispano la cosmovisión desarrollada asumió que la vida era una constante guerra espiritual. Esta percepción se componía de los conceptos de amor y violencia. Asimismo, esta comprensión fue incorporada a la política, en la que los conceptos anteriores se desarrollaron de diversas formas. La guerra en sus distintas formulaciones nos puede informar de las variantes políticas desarrolladas entre el amor y la violencia durante el Barroco hispano.

Leonardo Castellani

It is convenient to describe a quantum system at all times by means of a "history operator" $C$, encoding measurements and unitary time evolution between measurements. These operators naturally arise when computing the probability of measurement sequences, and generalize the "sum over position histories " of the Feynman path-integral. As we argue in the present note, this description has some computational advantages over the usual state vector description, and may help to clarify some issues regarding nonlocality of quantum correlations and collapse. A measurement on a system described by $C$ modifies the history operator, $C \rightarrow PC$, where $P$ is the projector corresponding to the measurement. We refer to this modification as "history operator collapse". Thus $C$ keeps track of the succession of measurements on a system, and contains all histories compatible with the results of these measurements. The collapse modifies the history content of $C$, and therefore modifies also the past (relative to the measurement), but never in a way to violate causality. Probabilities of outcomes are obtained as $Tr(C^\dagger P C)/Tr(C^\dagger C)$. A similar formula yields probabilities for intermediate measurements, and reproduces the result of the two-vector formalism in the case of given initial and final states. We apply the history operator formalism to a few examples: entangler circuit, Mach-Zehnder interferometer, teleportation circuit, three-box experiment. Not surprisingly, the propagation of coordinate eigenstates $|q\rangle$ is described by a history operator $C$ containing the Feynman path-integral.

Erik Høg

Here follow three reports covering different aspects of the early history from 1964 to 1980 of the Hipparcos satellite mission. The first report "Interviews about the creation of Hipparcos" contains interviews from 2017 with scientists about how the mission was conceived up to the begin of technical development. The second report "From TYCHO to Hipparcos 1975 to 1979" is about the Hipparcos development based on new material from my archive. From my 65 years dedicated to the development of astrometry, I argue that very special historical circumstances in Europe were decisive for the idea of space astrometry to become reality: Hipparcos did not just come because astrophysicists needed the data. The third report "Miraculous 1980 for Hipparcos" documents how the approval of the astrometric mission in January 1980 in competition with an astrophysical mission was only achieved with very great difficulty, even after an outstanding astrophysicist had presented overwhelming arguments that the astrometric mission would be scientifically much more important.

Haiming Tang, Paul Thomas, Haoran Xia

Gene gains and losses have shaped the gene repertoire of species since the universal last common ancestor to species today. Genes in extant species were gained at different historical times via de novo creation of new genes, duplication of existing genes or transfer from genes of another species (HGT), and get lost gradually. With the increasing number of sequenced genomes, some comparative analyses have been done to quantify the evolutionary history of gene gains and losses in restricted lineages like vertebrates, insects, fungi, plants and so on. Here, we have constructed and analyzed over 10,000 gene family trees to reconstruct the gene content of ancestral genomes at an unprecedented scale, covering hundreds of genomes across all domains of life. This is the most comprehensive genome-wide analysis of all events in gene evolutionary histories. We find that our results are largely consistent with earlier, less complete comparative studies on specific lineages such as the vertebrates, but find significant differences especially in recent evolutionary histories. We find that the rate of gene gain varies widely among branches of the species tree, and find that some periods of rapid gene duplication are associated with great extinctions in geological history.

Jesús Alonso Carballés