scholarly journals Directional dependence of the Unruh effect for spatially extended detectors

2020 ◽  
Vol 101 (2) ◽  
Author(s):  
Sanved Kolekar
Keyword(s):  
Unruh Effect ◽  
Directional Dependence ◽  
Spatially Extended

Walter Benjamin's media theory and the tradition of the media diaphana

2016 ◽  
Vol 7 (1) ◽  
pp. 9-26
Author(s):  
Antonio Somaini
Keyword(s):  
Sensory Experience ◽  
Media Theory ◽  
Depth Analysis ◽  
Spatially Extended ◽  
The Media ◽  
Aristotelian Tradition

"The article presents an in-depth analysis of Benjamin’s use of the German term Medium, in order to show how his entire media theory may be interpreted as centered on the interaction between the historically changing realm of the technical and material Apparate, and what he calls in the artwork essay the »Medium of perception«: the spatially extended environment, the atmosphere, the milieu, the Umwelt in which sensory experience occurs. This notion of »Medium of perception« is then located within the long, post-Aristotelian tradition of the media diaphana, whose traces can be found in the 1920s and 1930s in the writings of authors such as Béla Balázs, Fritz Heider, and László Moholy-Nagy. </br></br>Der Artikel präsentiert eine eingehende Analyse von Benjamins Gebrauch des deutschen Begriffs »Medium«, um zu zeigen, dass seine gesamte Medientheorie fokussiert ist auf die Interaktion zwischen dem historisch veränderlichen Bereich der technischen und materiellen Apparate einerseits und dem, was er in dem Kunstwerkaufsatz das »Medium der Wahrnehmung« nennt: die räumlich ausgedehnte Umgebung, die Atmosphäre, das Milieu, die Umwelt, in der sinnliche Wahrnehmung erfolgt. Dieser Begriff des »Mediums der Wahrnehmung« wird dann innerhalb der langen, nacharistotelischen Tradition der media diaphana verortet, deren Spuren in den 1920er und 1930er Jahren in den Schriften von Autoren wie Béla Balázs, Fritz Heider und László Moholy-Nagy zu finden sind."

scholarly journals Gaia-assisted discovery of a detached low-ionisation BAL quasar with very large ejection velocities

2020 ◽  
Vol 634 ◽  
pp. A111 ◽  
Author(s):  
J. P. U. Fynbo ◽  
P. Møller ◽  
K. E. Heintz ◽  
J. N. Burchett ◽  
L. Christensen ◽  
...  
Keyword(s):  
Emission Line ◽  
Absorption Line ◽  
Emission Lines ◽  
Broad Absorption ◽  
Broad Absorption Line ◽  
Red Edge ◽  
First Case ◽  
Bl Lac ◽  
Spatially Extended ◽  
Extended Emission

We report on the discovery of a peculiar broad absorption line (BAL) quasar identified in our Gaia-assisted survey of red quasars. The systemic redshift of this quasar was difficult to establish because of the absence of conspicuous emission lines. Based on deep and broad BAL troughs of at least Si IV, C IV, and Al III, a redshift of z = 2.41 was established under the assumption that the systemic redshift can be inferred from the red edge of the BAL troughs. However, we observe a weak and spatially extended emission line at 4450 Å that is most likely due to Lyman-α emission, which implies a systemic redshift of z = 2.66 if correctly identified. There is also evidence for the onset of Lyman-α forest absorption bluewards of 4450 Å and evidence for Hα emission in the K band consistent with a systemic redshift of z = 2.66. If this redshift is correct, the quasar is an extreme example of a detached low-ionisation BAL quasar. The BALs must originate from material moving with very large velocities ranging from 22 000 km s−1 to 40 000 km s−1. To our knowledge, this is the first case of a systemic-redshift measurement based on extended Lyman-α emission for a BAL quasar. This method could also be useful in cases of sufficiently distant BL Lac quasars without systemic-redshift information.

scholarly journals Unconventional singularities and energy balance in frictional rupture

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Efim A. Brener ◽  
Eran Bouchbinder
Keyword(s):  
Energy Balance ◽  
Square Root ◽  
Earthquake Physics ◽  
Macroscopic Theory ◽  
Scale Separation ◽  
Rate Dependent ◽  
Theoretical Predictions ◽  
Spatially Extended ◽  
Singularity Order ◽  
Square Root Singularity

AbstractA widespread framework for understanding frictional rupture, such as earthquakes along geological faults, invokes an analogy to ordinary cracks. A distinct feature of ordinary cracks is that their near edge fields are characterized by a square root singularity, which is intimately related to the existence of strict dissipation-related lengthscale separation and edge-localized energy balance. Yet, the interrelations between the singularity order, lengthscale separation and edge-localized energy balance in frictional rupture are not fully understood, even in physical situations in which the conventional square root singularity remains approximately valid. Here we develop a macroscopic theory that shows that the generic rate-dependent nature of friction leads to deviations from the conventional singularity, and that even if this deviation is small, significant non-edge-localized rupture-related dissipation emerges. The physical origin of the latter, which is predicted to vanish identically in the crack analogy, is the breakdown of scale separation that leads an accumulated spatially-extended dissipation, involving macroscopic scales. The non-edge-localized rupture-related dissipation is also predicted to be position dependent. The theoretical predictions are quantitatively supported by available numerical results, and their possible implications for earthquake physics are discussed.

scholarly journals Detectivity optimization to detect of ultraweak light fluxes with an EM-CCD as binary photon counter array

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ibtissame Khaoua ◽  
Guillaume Graciani ◽  
Andrey Kim ◽  
François Amblard
Keyword(s):  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
Photon Counting ◽  
Detection Methods ◽  
Strong Nonlinearity ◽  
Wide Range ◽  
Depth Analysis ◽  
Spatially Extended ◽  
Extended Sources ◽  
Photon Counting Mode

AbstractFor a wide range of purposes, one faces the challenge to detect light from extremely faint and spatially extended sources. In such cases, detector noises dominate over the photon noise of the source, and quantum detectors in photon counting mode are generally the best option. Here, we combine a statistical model with an in-depth analysis of detector noises and calibration experiments, and we show that visible light can be detected with an electron-multiplying charge-coupled devices (EM-CCD) with a signal-to-noise ratio (SNR) of 3 for fluxes less than $$30\,{\text{photon}}\,{\text{s}}^{ - 1} \,{\text{cm}}^{ - 2}$$ 30 photon s - 1 cm - 2 . For green photons, this corresponds to 12 aW $${\text{cm}}^{ - 2}$$ cm - 2 ≈ $$9{ } \times 10^{ - 11}$$ 9 × 10 - 11 lux, i.e. 15 orders of magnitude less than typical daylight. The strong nonlinearity of the SNR with the sampling time leads to a dynamic range of detection of 4 orders of magnitude. To detect possibly varying light fluxes, we operate in conditions of maximal detectivity $${\mathcal{D}}$$ D rather than maximal SNR. Given the quantum efficiency $$QE\left( \lambda \right)$$ Q E λ of the detector, we find $${ \mathcal{D}} = 0.015\,{\text{photon}}^{ - 1} \,{\text{s}}^{1/2} \,{\text{cm}}$$ D = 0.015 photon - 1 s 1 / 2 cm , and a non-negligible sensitivity to blackbody radiation for T > 50 °C. This work should help design highly sensitive luminescence detection methods and develop experiments to explore dynamic phenomena involving ultra-weak luminescence in biology, chemistry, and material sciences.

scholarly journals Modification to the Hawking temperature of a dynamical black hole by a flow-induced supertranslation

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Hsu-Wen Chiang ◽  
Yu-Hsien Kung ◽  
Pisin Chen
Keyword(s):  
Black Hole ◽  
Coordinate Transformation ◽  
Information Loss ◽  
Hawking Temperature ◽  
Asymptotic Region ◽  
Unruh Effect ◽  
Anisotropic Flow ◽  
Information Loss Paradox ◽  
History Of ◽  
Entire History

Abstract One interesting proposal to solve the black hole information loss paradox without modifying either general relativity or quantum field theory, is the soft hair, a diffeomorphism charge that records the anisotropic radiation in the asymptotic region. This proposal, however, has been challenged, given that away from the source the soft hair behaves as a coordinate transformation that forms an Abelian group, thus unable to store any information. To maintain the spirit of the soft hair but circumvent these obstacles, we consider Hawking radiation as a probe sensitive to the entire history of the black hole evaporation, where the soft hairs on the horizon are induced by the absorption of a null anisotropic flow, generalizing the shock wave considered in [1, 2]. To do so we introduce two different time-dependent extensions of the diffeomorphism associated with the soft hair, where one is the backreaction of the anisotropic null flow, and the other is a coordinate transformation that produces the Unruh effect and a Doppler shift to the Hawking spectrum. Together, they form an exact BMS charge generator on the entire manifold that allows the nonperturbative analysis of the black hole horizon, whose surface gravity, i.e. the Hawking temperature, is found to be modified. The modification depends on an exponential average of the anisotropy of the null flow with a decay rate of 4M, suggesting the emergence of a new 2-D degree of freedom on the horizon, which could be a way out of the information loss paradox.

scholarly journals Gradual regime shifts in spatially extended ecosystems

2012 ◽  
Vol 5 (4) ◽  
pp. 591-604 ◽  
Author(s):  
Golan Bel ◽  
Aric Hagberg ◽  
Ehud Meron
Keyword(s):  
Regime Shifts ◽  
Spatially Extended
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