کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8188850 | 1528842 | 2013 | 8 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Can the viscosity in astrophysical black hole accretion disks be close to its string theory bound?
ترجمه فارسی عنوان
آیا ویسکوزیته در دیسک های آکرو فیزیکی سیاه چاله تقریبا نزدیک به تئوری رشته آن است؟
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
فیزیک و نجوم
فیزیک هسته ای و انرژی بالا
چکیده انگلیسی
String theory and gauge/gravity duality suggest the lower bound of shear viscosity (η) to entropy density (s) for any matter to be â¼Î¼â/4ÏkB, when â and kB are reduced Planck and Boltzmann constants respectively and μ⩽1. Motivated by this, we explore η/s in black hole accretion flows, in order to understand if such exotic flows could be a natural site for the lowest η/s. Accretion flow plays an important role in black hole physics in identifying the existence of the underlying black hole. This is a rotating shear flow with insignificant molecular viscosity, which could however have a significant turbulent viscosity, generating transport, heat and hence entropy in the flow. However, in presence of strong magnetic field, magnetic stresses can help in transporting matter independent of viscosity, via celebrated Blandford-Payne mechanism. In such cases, energy and then entropy produces via Ohmic dissipation. In addition, certain optically thin, hot, accretion flows, of temperature â³109 K, may be favourable for nuclear burning which could generate/absorb huge energy, much higher than that in a star. We find that η/s in accretion flows appears to be close to the lower bound suggested by theory, if they are embedded by strong magnetic field or producing nuclear energy, when the source of energy is not viscous effects. A lower bound on η/s also leads to an upper bound on the Reynolds number of the flow.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Physics Letters B - Volume 721, Issues 1â3, 10 April 2013, Pages 151-158
Journal: Physics Letters B - Volume 721, Issues 1â3, 10 April 2013, Pages 151-158
نویسندگان
Banibrata Mukhopadhyay,