arXiv subjects

Jiun-Huei Proty Wu

Publications and source records attributed to Jiun-Huei Proty Wu.

At least 19 recordsLinked to original sources

arXiv2024

Quantum Cosmology on Quantum Computer

With physical quantum computers becoming increasingly accessible, research on their applications across various fields has advanced rapidly. In this paper, we present the first study of quantum cosmology conducted on physical quantum computers, employing a newly proposed Hybrid Quantum-Classical (HQC) algorithm rather than the commonly used Variational Quantum Eigensolver (VQE). Specifically, we solve a constrained Hamiltonian equation derived by quantizing the Friedmann equation in cosmology. To solve this constraint equation, H |psi> = 0, where H is a Hamiltonian operator and |psi> = |psi(theta)> is the wave function of phase angle theta describing the cosmic quantum state, we iteratively use the quantum computer to compute the eigenvalues of , while a classical computer manages the underlying probability density function within the Probabilistic Bisection Algorithm (PBA) to update theta until the solution of = 0 is achieved to a desired accuracy. Executing our algorithm on IBM's quantum computers, we attain a high-precision solution for theta, achieving approximately 1 percent error.

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arXiv2021

Detection of Gravitational Waves Using Bayesian Neural Networks

We propose a new model of Bayesian Neural Networks to not only detect the events of compact binary coalescence in the observational data of gravitational waves (GW) but also identify the full length of the event duration including the inspiral stage. This is achieved by incorporating the Bayesian approach into the CLDNN classifier, which integrates together the Convolutional Neural Network (CNN) and the Long Short-Term Memory Recurrent Neural Network (LSTM). Our model successfully detect all seven BBH events in the LIGO Livingston O2 data, with the periods of their GW waveforms correctly labeled. The ability of a Bayesian approach for uncertainty estimation enables a newly defined `awareness' state for recognizing the possible presence of signals of unknown types, which is otherwise rejected in a non-Bayesian model. Such data chunks labeled with the awareness state can then be further investigated rather than overlooked. Performance tests with 40,960 training samples against 512 chunks of 8-second real noise mixed with mock signals of various optimal signal-to-noise ratio $0 \leq ρ_\text{opt} \leq 18$ show that our model recognizes 90% of the events when $ρ_\text{opt} >7$ (100% when $ρ_\text{opt} >8.5$) and successfully labels more than 95% of the waveform periods when $ρ_\text{opt} >8$. The latency between the arrival of peak signal and generating an alert with the associated waveform period labeled is only about 20 seconds for an unoptimized code on a moderate GPU-equipped personal computer. This makes our model possible for nearly real-time detection and for forecasting the coalescence events when assisted with deeper training on a larger dataset using the state-of-art HPCs.

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arXiv2019

New Approach to Evolving Gravitational Waves in Loop Quantum Cosmology

With the observational advance in recent years, primordial gravitational waves (GWs), known as the tensor-mode cosmic perturbations, in the Loop Quantum Cosmology (LQC) are becoming testable and thus require better framework through which to bridge between the observations and the theories. In this work we present a new formalism that employs the transfer functions to bring the GWs from any epoch, even before the quantum bounce, to a later time, including the present. The evolutionary epochs considered here include the possible deflation, quantum bounce, and inflation. This formalism enables us to predict more accurately the GW power spectrum today. With the ADM formalism for the LQC background dynamics, our approach is equivalent to the commonly used Bogoliubov transformations for evolving the primordial GWs, but more transparent for discussions and easier to calculate due to its nature of being linear algebra dealing with linear perturbations. We utilize this advantage to have resolved the IR suppression problem. We also propose the field-free approximation for the effective mass in the quantum bounce epoch to largely improve the accuracy in the predicted GW power spectrum. Our transfer-function formalism is general in dealing with any linear problems, and thus expected to be equally useful under other context with linearity.

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arXiv2019

Time Asymmetry of Cosmic Background Evolution in Loop Quantum Cosmology

We discuss the asymmetry of cosmic background evolution in time with respect to the quantum bounce in the Loop Quantum Cosmology (LQC), employing the value of scalar field at the bounce $ϕ_{\rm B}$. We use the Chaotic and the $R^2$ potentials to demonstrate that a possible deflation before the bounce may counteract the inflation that is needed for resolving the cosmological conundrums, so a certain level of time asymmetry is required for the models in LQC. This $ϕ_{\rm B}$ is model dependent and closely related to the amounts of deflation and inflation, so we may use observations to confine $ϕ_{\rm B}$ and thus the model parameters. With further studies this formalism should be useful in providing an observational testbed for the LQC models.

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arXiv2016

AMiBA: Cluster Sunyaev-Zel'dovich Effect Observations with the Expanded 13-Element Array

The Yuan-Tseh Lee Array for Microwave Background Anisotropy (AMiBA) is a co-planar interferometer array operating at a wavelength of 3mm to measure the Sunyaev-Zeldovich effect (SZE) of galaxy clusters. In the first phase of operation -- with a compact 7-element array with 0.6m antennas (AMiBA-7) -- we observed six clusters at angular scales from 5\arcmin to 23\arcmin. Here, we describe the expansion of AMiBA to a 13-element array with 1.2m antennas (AMiBA-13), its subsequent commissioning, and our cluster SZE observing program. The most important changes compared to AMiBA-7 are (1) array re-configuration with baselines ranging from 1.4m to 4.8m covering angular scales from 2\arcmin to 11.5\arcmin, (2) thirteen new lightweight carbon-fiber-reinforced plastic (CFRP) 1.2m reflectors, and (3) additional correlators and six new receivers. From the AMiBA-13 SZE observing program, we present here maps of a subset of twelve clusters. In highlights, we combine AMiBA-7 and AMiBA-13 observations of Abell 1689 and perform a joint fitting assuming a generalized NFW pressure profile. Our cylindrically integrated Compton-y values for this cluster are consistent with the BIMA/OVRA, SZA, and Planck results. We report the first targeted SZE detection towards the optically selected galaxy cluster RCS J1447+0828, and we demonstrate the ability of AMiBA SZE data to serve as a proxy for the total cluster mass. Finally, we show that our AMiBA-SZE derived cluster masses are consistent with recent lensing mass measurements in the literature.

astro-ph.CO↗

arXiv2013

Platform Deformation Phase Correction for the AMiBA-13 Co-planar Interferometer

We present a new way to solve the platform deformation problem of co-planar interferometers. The platform of a co-planar interferometer can be deformed due to driving forces and gravity. A deformed platform will induce extra components into the geometric delay of each baseline, and change the phases of observed visibilities. The reconstructed images will also be diluted due to the errors of the phases. The platform deformations of The Yuan-Tseh Lee Array for Microwave Background Anisotropy (AMiBA) were modelled based on photogrammetry data with about 20 mount pointing positions. We then used the differential optical pointing error between two optical telescopes to fit the model parameters in the entire horizontal coordinate space. With the platform deformation model, we can predict the errors of the geometric phase delays due to platform deformation with given azimuth and elevation of the targets and calibrators. After correcting the phases of the radio point sources in the AMiBA interferometric data, we recover 50% - 70% flux loss due to phase errors. This allows us to restore more than 90% of a source flux. The method outlined in this work is not only applicable to the correction of deformation for other co-planar telescopes but also to single dish telescopes with deformation problems. This work also forms the basis of the upcoming science results of AMiBA-13.

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arXiv2011

Cosmic Microwave Background Delensing Revisited: Residual Biases and a Simple Fix

The delensing procedure is an effective tool for removing lensing-induced $B$-mode polarization in the Cosmic Microwave Background to allow for deep searches of primordial $B$-modes. However, the delensing algorithm existing in the literature breaks down if the target $B$-mode signals overlap significantly with the lensing $B$-mode ($\sim 300<l<2000$) in multipole-$l$ space. In this paper, we identify the cause of the breakdown to be correlations between the input $B$-map and the deflection field estimator ($EB$). The amplitude of this bias is quantified by numerical simulations and compared to the analytically derived functional form. We also propose a revised delensing procedure that circumvents the bias. While the newly identified bias does not affect the search of degree scale $B$-mode generated by tensor perturbations, the modified delensing algorithm makes it possible to perform deep searches of high-$l$ $B$-modes such as those generated by patchy reionization, cosmic strings, or rotation of polarization angles. Finally, we estimate how well future polarization experiments can do in detecting tensor- and cosmic string- generated $B$-mode after delensing and comment on different survey strategies.

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arXiv2010

1.2 Meter Shielded Cassegrain Antenna for Close-Packed Radio Interferometer

Interferometric millimeter observations of the cosmic microwave background and clusters of galaxies with arcmin resolutions require antenna arrays with short spacings. Having all antennas co-mounted on a single steerable platform sets limits to the overall weight. A 25 kg lightweight novel carbon-fiber design for a 1.2 m diameter Cassegrain antenna is presented. The finite element analysis predicts excellent structural behavior under gravity, wind and thermal load. The primary and secondary mirror surfaces are aluminum coated with a thin TiO$_2$ top layer for protection. A low beam sidelobe level is achieved with a Gaussian feed illumination pattern with edge taper, designed based on feedhorn antenna simulations and verified in a far field beam pattern measurement. A shielding baffle reduces inter-antenna coupling to below $\sim$ -135 dB. The overall antenna efficiency, including a series of efficiency factors, is estimated to be around 60%, with major losses coming from the feed spillover and secondary blocking. With this new antenna, a detection rate of about 50 clusters per year is anticipated in a 13-element array operation.

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arXiv2010

Contamination of the Central Sunyaev--Zel'dovich Decrements in AMiBA Galaxy Cluster Observations

We investigate the contamination of the Sunyaev--Zel'dovich (SZ) effect for six galaxy clusters, A1689, A1995, A2142, A2163, A2261, and A2390, observed by the Y. T. Lee Array for Microwave Background Anisotropy during 2007. With the range of baselines used, we find that the largest effect (of order 13%-50% of the central SZ flux density) comes from primary anisotropies in the cosmic microwave background and exceeds the thermal noise in all six cases. Contamination from discrete radio sources is estimated to be at a level of (3%-60%) of the central SZ flux density. We use the statistics of these contaminating sources to estimate and correct the errors in the measured SZ effects of these clusters.

astro-ph.CO↗

arXiv2010

AMiBA Wideband Analog Correlator

A wideband analog correlator has been constructed for the Yuan-Tseh Lee Array for Microwave Background Anisotropy. Lag correlators using analog multipliers provide large bandwidth and moderate frequency resolution. Broadband IF distribution, backend signal processing and control are described. Operating conditions for optimum sensitivity and linearity are discussed. From observations, a large effective bandwidth of around 10 GHz has been shown to provide sufficient sensitivity for detecting cosmic microwave background variations.

astro-ph.CO↗

arXiv2010

AMiBA: Sunyaev-Zel'dovich effect derived properties and scaling relations of massive galaxy clusters

The Sunyaev-Zel'dovich Effect (SZE) has been observed toward six massive galaxy clusters, at redshifts 0.091 \leq z \leq 0.322 in the 86-102 GHz band with the Y. T. Lee Array for Microwave Background Anisotropy (AMiBA). We modify an iterative method, based on the isothermal β-models, to derive the electron temperature T_e, total mass M_t, gas mass M_g, and integrated Compton Y within r_2500, from the AMiBA SZE data. Non-isothermal universal temperature profile (UTP) βmodels are also considered in this paper. These results are in good agreement with those deduced from other observations. We also investigate the embedded scaling relations, due to the assumptions that have been made in the method we adopted, between these purely SZE-deduced T_e, M_t, M_g and Y. Our results suggest that cluster properties may be measurable with SZE observations alone. However, the assumptions built into the pure-SZE method bias the results of scaling relation estimations and need further study.

astro-ph.CO↗

arXiv2009

AMiBA: scaling relations between the integrated Compton-y and X-ray derived temperature, mass, and luminosity

We investigate the scaling relations between the X-ray and the thermal Sunyaev-Zel'dovich Effect (SZE) properties of clusters of galaxies, using data taken during 2007 by the Y.T. Lee Array for Microwave Background Anisotropy (AMiBA) at 94 GHz for the six clusters A1689, A1995, A2142, A2163, A2261, and A2390. The scaling relations relate the integrated Compton-y parameter Y_{2500} to the X-ray derived gas temperature T_{e}, total mass M_{2500}, and bolometric luminosity L_X within r_{2500}. Our results for the power-law index and normalization are both consistent with the self-similar model and other studies in the literature except for the Y_{2500}-L_X relation, for which a physical explanation is given though further investigation may be still needed. Our results not only provide confidence for the AMiBA project but also support our understanding of galaxy clusters.

astro-ph.CO↗

arXiv2009

Platform Deformation Refined Pointing and Phase Correction for the AMiBA Hexapod Telescope

The Array for Microwave Background Anisotropy (AMiBA) is a radio interferometer for research in cosmology, currently operating 7 0.6m diameter antennas co-mounted on a 6m diameter platform driven by a hexapod mount. AMiBA is currently the largest hexapod telescope. We briefly summarize the hexapod operation with the current pointing error model. We then focus on the upcoming 13-element expansion with its potential difficulties and solutions. Photogrammetry measurements of the platform reveal deformations at a level which can affect the optical pointing and the receiver radio phase. In order to prepare for the 13-element upgrade, two optical telescopes are installed on the platform to correlate optical pointing tests. Being mounted on different locations, the residuals of the two sets of pointing errors show a characteristic phase and amplitude difference as a function of the platform deformation pattern. These results depend on the telescope's azimuth, elevation and polarization position. An analytical model for the deformation is derived in order to separate the local deformation induced error from the real hexapod pointing error. Similarly, we demonstrate that the deformation induced radio phase error can be reliably modeled and calibrated, which allows us to recover the ideal synthesized beam in amplitude and shape of up to 90% or more. The resulting array efficiency and its limits are discussed based on the derived errors.

astro-ph.IM↗

arXiv2009

AMiBA: Broadband Heterodyne CMB Interferometry

The Y. T. Lee Array for Microwave Background (AMiBA) has reported the first science results on the detection of galaxy clusters via the Sunyaev Zel'dovich effect. The science objectives required small reflectors in order to sample large scale structures (20') while interferometry provided modest resolutions (2'). With these constraints, we designed for the best sensitivity by utilizing the maximum possible continuum bandwidth matched to the atmospheric window at 86-102GHz, with dual polarizations. A novel wide-band analog correlator was designed that is easily expandable for more interferometer elements. MMIC technology was used throughout as much as possible in order to miniaturize the components and to enhance mass production. These designs will find application in other upcoming astronomy projects. AMiBA is now in operations since 2006, and we are in the process to expand the array from 7 to 13 elements.

astro-ph.CO↗

arXiv2009

AMiBA: System Performance

The Y.T. Lee Array for Microwave Background Anisotropy (AMiBA) started scientific operation in early 2007. This work describes the optimization of the system performance for the measurements of the Sunyaev-Zel'dovich effect for six massive galaxy clusters at redshifts $0.09 - 0.32$. We achieved a point source sensitivity of $63\pm 7$ mJy with the seven 0.6m dishes in 1 hour of on-source integration in 2-patch differencing observations. We measured and compensated for the delays between the antennas of our platform-mounted interferometer. Beam switching was used to cancel instrumental instabilities and ground pick up. Total power and phase stability were good on time scales of hours, and the system was shown to integrate down on equivalent timescales of 300 hours per baseline/correlation, or about 10 hours for the entire array. While the broadband correlator leads to good sensitivity, the small number of lags in the correlator resulted in poorly measured bandpass response. We corrected for this by using external calibrators (Jupiter and Saturn). Using Jupiter as the flux standard, we measured the disk brightness temperature of Saturn to be $149^{+5}_{-12}$ K.

astro-ph.IM↗

arXiv2009

The AMiBA Hexapod Telescope Mount

AMiBA is the largest hexapod astronomical telescope in current operation. We present a description of this novel hexapod mount with its main mechanical components -- the support cone, universal joints, jack screws, and platform -- and outline the control system with the pointing model and the operating modes that are supported. The AMiBA hexapod mount performance is verified based on optical pointing tests and platform photogrammetry measurements. The photogrammetry results show that the deformations in the inner part of the platform are less than 120 micron rms. This is negligible for optical pointing corrections, radio alignment and radio phase errors for the currently operational 7-element compact configuration. The optical pointing error in azimuth and elevation is successively reduced by a series of corrections to about 0.4 arcmin rms which meets our goal for the 7-element target specifications.

astro-ph.CO↗

arXiv2009

The Yuan-Tseh Lee Array for Microwave Background Anisotropy

The Yuan-Tseh Lee Array for Microwave Background Anisotropy (AMiBA) is the first interferometer dedicated to studying the cosmic microwave background (CMB) radiation at 3mm wavelength. The choice of 3mm was made to minimize the contributions from foreground synchrotron radiation and Galactic dust emission. The initial configuration of seven 0.6m telescopes mounted on a 6-m hexapod platform was dedicated in October 2006 on Mauna Loa, Hawaii. Scientific operations began with the detection of a number of clusters of galaxies via the thermal Sunyaev-Zel'dovich effect. We compare our data with Subaru weak lensing data in order to study the structure of dark matter. We also compare our data with X-ray data in order to derive the Hubble constant.

astro-ph↗

arXiv2009

Mass and Hot Baryons in Massive Galaxy Clusters from Subaru Weak Lensing and AMiBA SZE Observations

We present a multiwavelength analysis of a sample of four hot (T_X>8keV) X-ray galaxy clusters (A1689, A2261, A2142, and A2390) using joint AMiBA Sunyaev-Zel'dovich effect (SZE) and Subaru weak lensing observations, combined with published X-ray temperatures, to examine the distribution of mass and the intracluster medium (ICM) in massive cluster environments. Our observations show that A2261 is very similar to A1689 in terms of lensing properties. Many tangential arcs are visible around A2261, with an effective Einstein radius \sim 40 arcsec (at z \sim 1.5), which when combined with our weak lensing measurements implies a mass profile well fitted by an NFW model with a high concentration c_{vir} \sim 10, similar to A1689 and to other massive clusters. The cluster A2142 shows complex mass substructure, and displays a shallower profile (c_{vir} \sim 5), consistent with detailed X-ray observations which imply recent interaction. The AMiBA map of A2142 exhibits an SZE feature associated with mass substructure lying ahead of the sharp north-west edge of the X-ray core suggesting a pressure increase in the ICM. For A2390 we obtain highly elliptical mass and ICM distributions at all radii, consistent with other X-ray and strong lensing work. Our cluster gas fraction measurements, free from the hydrostatic equilibrium assumption, are overall in good agreement with published X-ray and SZE observations, with the sample-averaged gas fraction of = 0.133 \pm 0.027, for our sample = (1.2 \pm 0.1) \times 10^{15} M_{sun} h^{-1}. When compared to the cosmic baryon fraction f_b = Ω_b/Ω_m constrained by the WMAP 5-year data, this indicates /f_b = 0.78 \pm 0.16, i.e., (22 \pm 16)% of the baryons are missing from the hot phase of clusters.

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