In Defense of the Standard Picture: The Basic Challenge

Ratio Juris ◽  
2021 ◽  
Author(s):  
Larry Alexander
Keyword(s):  
Standard Picture

scholarly journals Millisecond Pulsars

1989 ◽  
Vol 8 ◽  
pp. 161-165
Author(s):  
J.H. Krolik
Keyword(s):  
Neutron Star ◽  
Stellar Evolution ◽  
Close Binary ◽  
Millisecond Pulsar ◽  
Millisecond Pulsars ◽  
Physical Conditions ◽  
Cast Doubt ◽  
Standard Picture ◽  
The Universe ◽  
New System

AbstractMillisecond pulsars are intrinsically interesting because they illustrate some of the most extreme physical conditions to be found anywhere in the Universe, and because their evolution exhibits several stages of great drama. It had been widely believed for several years that spin-up of an old neutron star by accretion from a close stellar companion explained their fast rotation, but the absence of companions in several cases cast doubt on that picture. This spring a millisecond pulsar in a close binary was discovered in which the companion appears to be evaporating, thus reconciling the existence of lone millisecond pulsars with the standard picture. Ongoing observations of this new system, and complementary calculations, promise to answer many of the questions remaining about this dramatic phase in stellar evolution.

The Place of Expert Intuition in Philosophy

2020 ◽  
pp. 184-207
Author(s):  
Elijah Chudnoff
Keyword(s):  
Current Practice ◽  
Philosophical Methodology ◽  
Traditional Philosophy ◽  
Standard Picture ◽  
Intuitive Judgments ◽  
Historical Antecedents ◽  
Expertise Defense

The Standard Picture of philosophical methodology includes the following claims: (A) Intuitive judgments form an epistemically distinctive kind; (B) Intuitive judgments play an epistemically privileged role in philosophical methodology; (C) If intuitive judgments play an epistemically privileged role in philosophical methodology, then their role is to be taken as given inputs into generally accepted forms of reasoning; (D) Philosophical methodology is reasonable. Negative experimental philosophers accept claims (A), (B), and (C), but challenge (D). This chapter develops a variant on the expertise defense of traditional philosophy. The defense hinges on denying (C) in the Standard Picture: philosophers do not treat their intuitions as data; they treat their intuitions as observations that can be improved through reasoning. The chapter explores both historical antecedents in the rationalist tradition, and descriptive accuracy with respect to current practice.

scholarly journals On the opening angle of magnetized jets from neutron-star mergers: the case of GRB170817A

2020 ◽  
Vol 495 (4) ◽  
pp. 3780-3787 ◽  
Author(s):  
Antonios Nathanail ◽  
Ramandeep Gill ◽  
Oliver Porth ◽  
Christian M Fromm ◽  
Luciano Rezzolla
Keyword(s):  
Neutron Star ◽  
Gamma Ray ◽  
Initial Conditions ◽  
Observation Angle ◽  
Opening Angle ◽  
Binary Neutron Star ◽  
Best Fitting ◽  
Standard Picture ◽  
General Relativistic ◽  
Star Binary

ABSTRACT The observations of GW170817/GRB170817A have confirmed that the coalescence of a neutron-star binary is the progenitor of a short gamma-ray burst (GRB). In the standard picture of a short GRB, a collimated highly relativistic outflow is launched after merger and it successfully breaks out from the surrounding ejected matter. Using initial conditions inspired from numerical-relativity binary neutron-star merger simulations, we have performed general-relativistic hydrodynamic (HD) and magnetohydrodynamic (MHD) simulations in which the jet is launched and propagates self-consistently. The complete set of simulations suggests that: (i) MHD jets have an intrinsic energy and velocity polar structure with a ‘hollow core’ subtending an angle θcore ≈ 4°–5° and an opening angle of θjet > ≳ 10°; (ii) MHD jets eject significant amounts of matter and two orders of magnitude more than HD jets; (iii) the energy stratification in MHD jets naturally yields the power-law energy scaling E(> Γβ) ∝ (Γβ)−4.5; (iv) MHD jets provide fits to the afterglow data from GRB170817A that are comparatively better than those of the HD jets and without free parameters; and (v) finally, both of the best-fitting HD/MHD models suggest an observation angle θobs ≃ 21° for GRB170817A.

scholarly journals Alternative Solutions to Big Bang Nucleosynthesis

2000 ◽  
Vol 198 ◽  
pp. 25-34 ◽  
Author(s):  
Hannu Kurki-Suonio
Keyword(s):  
Neutrino Physics ◽  
Early Universe ◽  
Big Bang ◽  
Big Bang Nucleosynthesis ◽  
Standard Picture ◽  
Alternative Solutions

Standard big bang nucleosynthesis (SBBN) has been remarkably successful, and it may well be the correct and sufficient account of what happened. However, interest in variations from the standard picture come from two sources: First, big bang nucleosynthesis can be used to constrain physics of the early universe. Second, there may be some discrepancy between predictions of SBBN and observations of abundances. Various alternatives to SBBN include inhomogeneous nucleosynthesis, nucleosynthesis with antimatter, and nonstandard neutrino physics.

scholarly journals LOW-MAGNETIC-FIELD MAGNETARS

2013 ◽  
Vol 22 (13) ◽  
pp. 1330024 ◽  
Author(s):  
ROBERTO TUROLLA ◽  
PAOLO ESPOSITO
Keyword(s):  
Magnetic Field ◽  
Magnetic Energy ◽  
Strong Field ◽  
Radio Pulsars ◽  
X Ray ◽  
Soft Gamma Repeaters ◽  
Dipole Magnetic Field ◽  
Standard Picture ◽  
Observational Status ◽  
Low Magnetic Field

It is now widely accepted that soft gamma repeaters and anomalous X-ray pulsars are the observational manifestations of magnetars, i.e. sources powered by their own magnetic energy. This view was supported by the fact that these "magnetar candidates" exhibited, without exception, a surface dipole magnetic field (as inferred from the spin-down rate) in excess of the electron critical field (≃ 4.4×1013 G). The recent discovery of fully qualified magnetars, SGR 0418+5729 and Swift J1822.3-1606, with dipole magnetic field well in the range of ordinary radio pulsars posed a challenge to the standard picture, showing that a very strong field is not necessary for the onset of magnetar activity (chiefly bursts and outbursts). Here we summarize the observational status of the low-magnetic-field magnetars and discuss their properties in the context of the mainstream magnetar model and its main alternatives.

scholarly journals Conformal invariance and the metrication of the fundamental forces

2016 ◽  
Vol 25 (12) ◽  
pp. 1644003 ◽  
Author(s):  
Philip D. Mannheim
Keyword(s):  
String Theory ◽  
Conformal Invariance ◽  
Vector Fields ◽  
Axial Vector ◽  
Gravitational Theory ◽  
Einstein Gravity ◽  
Conformal Gravity ◽  
Yang Mills ◽  
Standard Picture ◽  
Fundamental Forces

We revisit Weyl’s metrication (geometrization) of electromagnetism. We show that by making Weyl’s proposed geometric connection be pure imaginary, not only are we able to metricate electromagnetism, an underlying local conformal invariance makes the geometry be strictly Riemannian and prevents observational gravity from being complex. Via torsion, we achieve an analogous metrication for axial-vector fields. We generalize our procedure to Yang–Mills theories, and achieve a metrication of all the fundamental forces. Only in the gravity sector does our approach differ from the standard picture of fundamental forces, with our approach requiring that standard Einstein gravity be replaced by conformal gravity. We show that quantum conformal gravity is a consistent and unitary quantum gravitational theory, one that, unlike string theory, only requires four spacetime dimensions.

scholarly journals SIGNATURES OF EXOTIC HADRONS

2011 ◽  
Vol 26 (29) ◽  
pp. 4855-4879
Author(s):  
FRANCESCO RENGA
Keyword(s):  
Quantum Chromodynamics ◽  
Hadron Collider ◽  
Fundamental Symmetries ◽  
Hadron Spectroscopy ◽  
The Past ◽  
Standard Picture ◽  
Strong Forces ◽  
Exotic Hadrons

Hadron spectroscopy represented in the past a major tool for understanding the fundamental symmetries of strong forces. More recently, the interest on this topic has been revitalized by the discovery of new quarkonium-like resonances, that do not fit in the standard picture and whose understanding could improve our mastery of quantum chromodynamics. I review here the experimental signatures of these exotic hadrons, at present and future e+e- and hadron collider experiments.

scholarly journals Facilitated Dissociation of Transcription Factors from Single DNA Binding Sites

2017 ◽  
Author(s):  
Ramsey I. Kamar ◽  
Edward J. Banigan ◽  
Aykut Erbas ◽  
Rebecca D. Giuntoli ◽  
Monica Olvera de la Cruz ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Binding Site ◽  
Single Molecule ◽  
Binding Sites ◽  
Binding Kinetics ◽  
General Mechanism ◽  
Dissociation Kinetics ◽  
Dna Binding Sites ◽  
Standard Picture ◽  
Dynamics Simulations

ABSTRACTThe binding of transcription factors (TFs) to DNA controls most aspects of cellular function, making the understanding of their binding kinetics imperative. The standard description of bimolecular interactions posits TF off-rates are independent of TF concentration in solution. However, recent observations have revealed that proteins in solution can accelerate the dissociation of DNA-bound proteins. To study the molecular basis of facilitated dissociation (FD), we have used single-molecule imaging to measure dissociation kinetics of Fis, a key E. coli TF and major bacterial nucleoid protein, from single dsDNA binding sites. We observe a strong FD effect characterized by an exchange rate ∽1 × 104 M-1s-1, establishing that FD of Fis occurs at the single-binding-site level, and we find that the off-rate saturates at large Fis concentrations in solution. While spontaneous (i.e., competitor-free) dissociation shows a strong salt dependence, we find that facilitated dissociation depends only weakly on salt. These results are quantitatively explained by a model in which partially dissociated bound proteins are susceptible to invasion by competitor proteins in solution. We also report FD of NHP6A, a yeast TF whose structure differs significantly from Fis. We further perform molecular dynamics simulations, which indicate that FD can occur for molecules that interact far more weakly than those we have studied. Taken together, our results indicate that FD is a general mechanism assisting in the local removal of TFs from their binding sites and does not necessarily require cooperativity, clustering, or binding site overlap.SIGNIFICANCE STATEMENTTranscription factors (TFs) control biological processes by binding and unbinding to DNA. Therefore it is crucial to understand the mechanisms that affect TF binding kinetics. Recent studies challenge the standard picture of TF binding kinetics by demonstrating cases of proteins in solution accelerating TF dissociation rates through a facilitated dissociation (FD) process. Our study shows that FD can occur at the level of single binding sites, without the action of large protein clusters or long DNA segments. Our results quantitatively support a model of FD in which competitor proteins invade partially dissociated states of DNA-bound TFs. FD is expected to be a general mechanism for modulating gene expression by altering the occupancy of TFs on the genome.Author ContributionsRamsey I. Kamardesigned research, performed research, contributed new reagents/analytic tools, analyzed data, wrote the paperEdward J. Banigandesigned research, performed research, contributed new reagents/analytic tools, analyzed data, wrote the paperAykut Erbasdesigned research, performed research, contributed new reagents/analytic tools, analyzed data, wrote the paperRebecca D. Giuntolidesigned research, performed research, contributed new reagents/analytic tools, analyzed data, wrote the paperMonica Olvera de la Cruzdesigned research, performed research, wrote the paperReid C. Johnsondesigned research, performed research, contributed new reagents/analytic tools, analyzed data, wrote the paperJohn F. Markodesigned research, performed research, contributed new reagents/analytic tools, analyzed data, wrote the paper

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