Hasil untuk "History (General)"

Julie Hugo, M. Ganguli

P. Juola

J. Bonta, Moira A Law, Karl Hanson

V. Propp, Svatava Pirkova-Jakobson, L. Scott

Professor Dr. Friedrich Ruttner

P. Taylor, P. Hirst, Grahame F. Thompson

John D. Anderson

L. Huddy

M. Berry

S. Leroueil, P. Vaughan

M. Goodchild, Linna Li

G. Domènech

We provide a review on the state-of-the-art of gravitational waves induced by primordial fluctuations, so-called induced gravitational waves. We present the intuitive physics behind induced gravitational waves and we revisit and unify the general analytical formulation. We then present general formulas in a compact form, ready to be applied. This review places emphasis on the open possibility that the primordial universe experienced a different expansion history than the often assumed radiation dominated cosmology. We hope that anyone interested in the topic will become aware of current advances in the cosmology of induced gravitational waves, as well as becoming familiar with the calculations behind.

James H. Stronge

Todd L Graves, A. Karr, J. Marron et al.

K. McAuley, Sheila M. Williams, J. Mann et al.

A. Danese, T. Moffitt, C. Pariante et al.

Keith Andrew, Eric V. Steinfelds, Kristopher A. Andrew

Lorentzian topology change may be resolved into an ordered sequence of localized, orientation-sensitive operations rather than treated solely as a global transition between spatial manifolds. We develop a generator-history framework in which topology-changing spacetimes are represented algebraically as compositions of elementary local events, independent of dynamics, quantization, or anomaly inflow. Braid groups arise as the minimal realization of ordered, invertible pairwise exchanges, while higher-valence generators extend the construction to networked processes. Within this framework we identify parity-odd conformal curvature as the unique nontrivial local curvature pseudoscalar (without derivatives) capable of aggregating oriented generator content in four-dimensional Lorentzian vacuum geometry. The dual Weyl contraction changes sign under orientation reversal and therefore isolates chiral generator accumulation, while parity-even curvature scalars are insensitive to such structure. The associated spacetime integral functions as a covariant geometric diagnostic of chiral topology change that depends on generator histories and does not descend to endpoint-only equivalence classes obtained by Markov-type coarse-graining. The resulting picture isolates a pre-quantum geometric layer beneath spectral asymmetry: oriented generator dynamics induce parity-odd curvature compatible with the Pontryagin density appearing in the Atiyah Patodi Singer index theorem yet remains defined entirely within classical Lorentzian geometry. This framework clarifies the algebraic and geometric substrate underlying chiral topology change without introducing new gravitational dynamics or topological invariants.

Celina DeBiasio, Jillian Dhawan, Quentin Nakonechny et al.

Leiomyosarcoma (LMS) of the skin is a rare malignant neoplasm that can have varied clinical presentations, even mimicking benign lesions, making diagnosis challenging. We describe a 74-year-old male with a history of subcutaneous LMS of the left leg treated successfully with surgery, chemotherapy, and radiation over 10 years prior, who presented with an incidental papule on the lower back resembling an accessory nipple. Biopsy revealed a spindle cell tumour with diffuse smooth muscle actin and desmin positivity and a high Ki-67 index, consistent with a non-metastatic subcutaneous LMS. Wide local excision confirmed dermal and subcutaneous involvement with negative margins. This case is notable for the occurrence of two distinct primary LMS lesions more than a decade apart, underscoring the importance of long-term surveillance in high-risk patients. Given the potential for recurrence or metastasis, careful histopathologic evaluation and ongoing monitoring remain critical in the management of LMS.

Hisaaki Shinkai, Masao Takamoto, Hidetoshi Katori

Optical lattice clocks (OLCs) enable us to measure time and frequency with a fractional uncertainty at $10^{-18}$ level, which is 2 orders of magnitude better than Cs clocks. In this article, after briefly reviewing OLCs and the history of testing the fundamental principles of general relativity, we report our experiments of measuring the gravitational redshift between RIKEN and The University of Tokyo, and at Tokyo Skytree using transportable OLCs. We also discuss a couple of future applications of OLCs, such as detecting gravitational waves in space and relativistic geodesy. The possibility of testing second-order parametrized post-Newtonian potential around the Earth is also mentioned.

Emanuele Bottazzi, Mikhail G. Katz

We apply Nancy Cartwright's distinction between theories and basic models to explore the history of rival approaches to modeling a notion of chance for an ideal uniform physical process known as a fair spinner. This process admits both Archimedean and non-Archimedean models. Advocates of Archimedean models maintain that the fair spinner should satisfy hypotheses such as invariance with respect to rotations by an arbitrary real angle, and assume that the optimal mathematical tool in this context is the Lebesgue measure. Others argue that invariance with respect to all real rotations does not constitute an essential feature of the underlying physical process, and could be relaxed in favor of regularity. We show that, working in ZFC, no subset of the commonly assumed hypotheses determines a unique model, suggesting that physically based intuitions alone are insufficient to pin down a unique mathematical model. We provide a rebuttal of recent criticisms of non-Archimedean models by Parker and Pruss.