14.Energetic Cosmos LaboratoryECL is an astrophysics laboratory founded by Nobel Prize Winner George Smoot in 2017, with the goal to understand fundamental problems in physics and astrophysics and contribute to the technical know-how and innovation ecosystem of NU.http://nur.nu.edu.kz:80/handle/123456789/63712022-08-19T02:04:13Z2022-08-19T02:04:13ZON THE DUALITY OF SCHWARZSCHILD-DE SITTER SPACETIME AND MOVING MIRRORFernandez-Silvestre, DiegoFoo, JoshuaGood, Michael R.R.http://nur.nu.edu.kz:80/handle/123456789/65142022-07-22T21:00:45Z2022-01-01T00:00:00ZON THE DUALITY OF SCHWARZSCHILD-DE SITTER SPACETIME AND MOVING MIRROR
Fernandez-Silvestre, Diego; Foo, Joshua; Good, Michael R.R.
The Schwarzschild-de Sitter (SdS) metric is the simplest spacetime solution in general relativity with both a
black hole event horizon and a cosmological event horizon. Since the Schwarzschild metric is the most simple
solution of Einstein’s equations with spherical symmetry and the de Sitter metric is the most simple solution
of Einstein’s equations with a positive cosmological constant, the combination in the SdS metric defines an
appropriate background geometry for semi-classical investigation of Hawking radiation with respect to past and
future horizons. Generally, the black hole temperature is larger than that of the cosmological horizon, so there is
heat flow from the smaller black hole horizon to the larger cosmological horizon, despite questions concerning
the definition of the relative temperature of the black hole without a measurement by an observer sitting in
an asymptotically flat spacetime. Here we investigate the accelerating boundary correspondence (ABC) of the
radiation in SdS spacetime without such a problem. We have solved for the boundary dynamics, energy flux
and asymptotic particle spectrum. The distribution of particles is globally non-thermal while asymptotically the
radiation reaches equilibrium
2022-01-01T00:00:00ZBLACK HOLE HOOKEAN LAW AND THERMODYNAMIC FRAGMENTATION: INSIGHTS FROM THE MAXIMUM FORCE CONJECTURE AND RUPPEINER GEOMETRYGennaro, Sofia DiGood, Michael R. R.Ong, Yen Chinhttp://nur.nu.edu.kz:80/handle/123456789/64702022-07-20T21:00:18Z2022-01-01T00:00:00ZBLACK HOLE HOOKEAN LAW AND THERMODYNAMIC FRAGMENTATION: INSIGHTS FROM THE MAXIMUM FORCE CONJECTURE AND RUPPEINER GEOMETRY
Gennaro, Sofia Di; Good, Michael R. R.; Ong, Yen Chin
We show that the notion of “Hookean law” F = kx, suitably defined in asymptotically flat singly spinning
Myers-Perry black hole space-times in dimensions d 5, is related to the Emparan-Myers fragmentation
(splitting of a black hole into two becomes thermodynamically preferable). Specifically, the values of black hole
parameters when fragmentation occurs correspond to the maximal value of F. Furthermore this always happens
before F reaches 1/4 in Planck units. These results suggest that a version of “maximum force conjecture” may be
relevant for black hole thermodynamics. We also relate these findings to the Ruppeiner thermodynamic geometry
of these black holes and speculate on the implications for the underlying microstructures of black hole horizons.
2022-01-01T00:00:00ZDETERMINING MODEL-INDEPENDENT H0 AND CONSISTENCY TESTSLiao, KaiShafieloo, ArmanKeeley, Ryan E.Linder, Eric V.http://nur.nu.edu.kz:80/handle/123456789/64452022-07-15T21:00:15Z2020-01-01T00:00:00ZDETERMINING MODEL-INDEPENDENT H0 AND CONSISTENCY TESTS
Liao, Kai; Shafieloo, Arman; Keeley, Ryan E.; Linder, Eric V.
We determine the Hubble constant H0 precisely (2.3% uncertainty) in a manner independent of
cosmological model through Gaussian process regression, using strong lensing and supernova data.
Strong gravitational lensing of a variable source can provide a time-delay distance D∆t and angular
diameter distance to the lens Dd. These absolute distances can anchor Type Ia supernovae, which
give an excellent constraint on the shape of the distance-redshift relation. Updating our previous
results to use the H0LiCOW program’s milestone dataset consisting of six lenses, four of which have
both D∆t and Dd measurements, we obtain H0 = 72.8
+1.6
−1.7
km/s/Mpc for a flat universe and H0 =
77.3
+2.2
−3.0
km/s/Mpc for a non-flat universe. We carry out several consistency checks on the data
and find no statistically significant tensions, though a noticeable redshift dependence persists in a
particular systematic manner that we investigate. Speculating on the possibility that this trend of
derived Hubble constant with lens distance is physical, we show how this can arise through modified
gravity light propagation, which would also impact the weak lensing σ8 tension
2020-01-01T00:00:00ZCHARACTERIZATION OF A HIGH EFFICIENCY SILICON PHOTOMULTIPLIER FOR MILLISECOND TO SUB-MICROSECOND ASTROPHYSICAL TRANSIENTLi, SiyangSmoot, George F.http://nur.nu.edu.kz:80/handle/123456789/63922022-07-11T21:00:36Z2020-01-01T00:00:00ZCHARACTERIZATION OF A HIGH EFFICIENCY SILICON PHOTOMULTIPLIER FOR MILLISECOND TO SUB-MICROSECOND ASTROPHYSICAL TRANSIENT
Li, Siyang; Smoot, George F.
We characterized the S14160-3050HS Multi-Pixel Photon Counter (MPPC), a high efficiency, single channel
silicon photomultiplier manufactured by Hamamatsu Photonics K.K. All measurements were performed at a
room temperature of (23.0 ± 0.3) °C. We obtained an I-V curve and used relative derivatives to find a breakdown
voltage of 38.88 V. At a 3 V over voltage, we find a dark count rate of 1.08 MHz, crosstalk probability of 21
%, photon detection efficiency of 55 % at 450 nm, and saturation at 1.0x1011 photons per second. The S14160-
3050HS MPPC is a candidate detector for the Ultra-Fast Astronomy (UFA) telescope which will characterize
the optical (320 nm - 650 nm) sky in the millisecond to sub-microsecond timescales using two photon counting
arrays operated in coincidence on the 0.7 meter Nazarbayev University Transient Telescope at the Assy-Turgen
Astrophysical Observatory (NUTTelA-TAO) located near Almaty, Kazakhstan. We discuss advantages and
disadvantages of using the S14160-3050HS MPPC for the UFA telescope and future ground-based telescopes in
sub-second time domain astrophysics.
2020-01-01T00:00:00ZON-SKY SILICON PHOTOMULTIPLIER DETECTOR PERFORMANCE MEASUREMENTS FOR MILLISECOND TO SUB-MICROSECOND OPTICAL SOURCE VARIABILITY STUDIESLau, Albert Wai KitShafiee, MehdiSmoot, George F.Grossan, BruceLi, SiyangMaksut, Zhanathttp://nur.nu.edu.kz:80/handle/123456789/63912022-07-11T21:00:33Z2020-01-01T00:00:00ZON-SKY SILICON PHOTOMULTIPLIER DETECTOR PERFORMANCE MEASUREMENTS FOR MILLISECOND TO SUB-MICROSECOND OPTICAL SOURCE VARIABILITY STUDIES
Lau, Albert Wai Kit; Shafiee, Mehdi; Smoot, George F.; Grossan, Bruce; Li, Siyang; Maksut, Zhanat
In our Ultra-Fast Astronomy (UFA) program, we aim to improve measurements of variability of astro nomical targets on millisecond and shorter time scales. In this work, we present initial on-sky measurements of the
performance of silicon photomultiplier detectors (SiPMs) for UFA. We mounted two different SiPMs at the focal plane
of the 0.7-meter aperture Nazarbayev University Transient Telescope at the Assy-Turgen Astrophysical Observatory
(NUTTelA-TAO), with no filter in front of the detector. The 3mm × 3mm SiPM single-channel detectors have a
field of view of 2.27160 × 2.27160
. During the nights of 2019 October 28-29, we measured sky background, bright
stars, and an artificial source with a 100Hz flashing frequency. We compared detected SiPM counts with Gaia satellite
G-band flux values to show that our SiPMs have a linear response. With our two SiPMs (models S14520-3050VS and
S14160-3050HS), we measured a dark current of ∼130 and ∼85 kilo counts per second (kcps), and a sky background
of ∼201 and ∼203 kcps, respectively. We measured an intrinsic crosstalk of 10.34% and 10.52% and derived a 5σ
sensitivity of 13.9 and 14.0 Gaia G-band magnitude for 200ms exposures, for the two detectors respectively. For a 10
µs window, and allowing a false alarm rate of once per 100 nights, we derived a sensitivity of 22 detected photons, or
6 Gaia G-band magnitudes. For nanosecond timescales, our detection is limited by crosstalk to 12 detected photons,
which corresponds to a fluence of ∼155 photons per square meter
2020-01-01T00:00:00ZTHE MIRROR AT THE EDGE OF THE UNIVERSE: REFLECTIONS ON AN ACCELERATED BOUNDARY CORRESPONDENCE WITH DE SITTER COSMOLOGYZhakenuly, AbayGood, Michael R.R.Linder, Eric V.http://nur.nu.edu.kz:80/handle/123456789/63792022-07-07T21:00:18Z2020-01-01T00:00:00ZTHE MIRROR AT THE EDGE OF THE UNIVERSE: REFLECTIONS ON AN ACCELERATED BOUNDARY CORRESPONDENCE WITH DE SITTER COSMOLOGY
Zhakenuly, Abay; Good, Michael R.R.; Linder, Eric V.
An accelerated boundary correspondence (ABC) is solved for the de Sitter moving mirror cos mology. The beta Bogoliubov coefficients reveal the particle spectrum is a Planck distribution with
temperature inversely proportional to horizon radius. The quantum stress-tensor indicates a con stant emission of energy flux consistent with eternal equilibrium, while the total energy carried
by the particles remains finite. The curved spacetime transformation to flat spacetime with an
accelerated boundary is illustrated, and also shown for Anti-de Sitter (AdS) spacetime
2020-01-01T00:00:00Z