Cosmological Implications of 5-dimensional Brans-Dicke Theory (2009)
Qiang, Li-e, Gong, Yan, Ma, Yongge, Chen, Xuelei
The five dimensional Brans-Dicke theory naturally provides two scalar fields by the Killing reduction mechanism. These two scalar fields could account for the accelerated expansion of the universe....
Cosmology with Photometric Surveys of Type Ia Supernovae (2009)
Gong, Yan, Cooray, Asantha, Chen, Xuelei
We discuss the extent to which photometric measurements alone can be used to identify Type Ia supernovae (SNIa) and to determine redshift and other parameters of interest for cosmological studies. We...
The contribution of the IGM and minihalos to the 21 cm signal of reionization (2009)
Yue, Bin, Ciardi, Benedetta, Scannapieco, Evan, Chen, Xuelei
We study the statistical properties of the cosmological 21 cm signal from both the intergalactic medium (IGM) and minihalos, using a reionization simulation that includes a self--consistent treatment...
Xu, Yidong, Chen, Xuelei, Fan, Zuhui, Trac, Hy, Cen, Renyue
Using high redshift radio sources as background, the 21cm forest observations probe the neutral hydrogen absorption signatures of early structures along the lines of sight. Directly sensitive to the...
Primordial Non-Gaussianity from LAMOST Surveys (2009)
Gong, Yan, Wang, Xin, Zheng, Zheng, Chen, Xuelei
The primordial non-Gaussianity (PNG) in matter density perturbation is a very powerful probe of the physics of the very early Universe. The local PNG can induce a distinct scale-dependent bias on the...
Cosmic microwave background with Brans-Dicke Gravity: I. Covariant Formulation (2009)
Wu, Fengquan, Qiang, Li-e, Wang, Xin, Chen, Xuelei
In the covariant cosmological perturbation theory, a 1+3 decomposition ensures that all variables in the frame-independent equations are covariant, gauge-invariant and have clear physical...
Using the covariant formalism developed in a companion paper (paper I), we derive observational constraint on the Brans-Dicke model in a flat FLRW universe with cosmological constant and cold dark...
Dark matter annihilation and non-thermal Sunyaev-Zel'dovich effect: I. galaxy cluster (2009)
Yuan, Qiang, Bi, Xiaojun, Huang, Feng, Chen, Xuelei
In this work we calculate the Sunyaev-Zel'dovich (SZ) effect due to the $e^+e^-$ from dark matter (DM) annihilation in galaxy clusters. Two candidates of DM particle, (1) the weakly-interacting...
Couplings between holographic dark energy and dark matter (2009)
Ma, Yinzhe, Gong, Yan, Chen, Xuelei
We consider the interaction between dark matter and dark energy in the framework of holographic dark energy, and propose a natural and physically plausible form of interaction, in which the...
The contribution of the IGM and minihaloes to the 21-cm signal of reionization (2009)
Yue, Bin, Ciardi, Benedetta, Scannapieco, Evan, Chen, Xuelei
What is the fate of a black hole embedded in an expanding universe? (2008)
Faraoni, Valerio, Gao, Changjun, Chen, Xuelei, Shen, You-Gen
Within a large class of exact solutions of the Einstein equations describing a black hole embedded in a Friedmann universe it is shown that, under certain assumptions, only those with comoving...
Alignment between the host and the nearest neighbor Groups (2008)
Wang, Yougang, Park, Changbom, Yang, Xiaohu, Choi, Yun-Young, Chen, Xuelei
We measure four different types of alignment signals using the galaxy groups of the Sloan Digital Sky Survey Data Release 4 to probe the impact of large scale environment on the distribution of...
Wang, Xin, Chen, Xuelei, Zheng, Zheng, Wu, Fengquan, Zhang, Pengjie, Zhao, Yongheng
The Large Area Multi-Object Spectroscopic Telescope (LAMOST) is a dedicated spectroscopic survey telescope being built in China, with an effective aperture of 4 meters and equiped with 4000 fibers....
Effects of correlation between merging steps on the global halo formation (2008)
Pan, Jun, Wang, Yougang, Chen, Xuelei, Teodoro, Luis
The excursion set theory of halo formation is modified by adopting the fractional Brownian motion, to account for possible correlation between merging steps. We worked out analytically the...
Cosmological constraints on unparticle dark matter (2008)
In unparticle dark matter (unmatter) models the equation of state of the unmatter is given by $p=\rho/(2d_U+1)$, where $d_U$ is the scaling factor. Unmatter with such equations of state would have a...
Cosmological Constraints on Invisible Decay of Dark Matter (2008)
The cold dark matter may be in a meta-stable state and decays to other particles with a very long lifetime. If the decaying products of the dark matter are weakly interacting, e.g. neutrinos, then it...
Does the mass of a black hole decrease due to the accretion of phantom energy (2008)
Gao, Changjun, Chen, Xuelei, Faraoni, Valerio, Shen, You-Gen
According to Babichev et al., the accretion of a phantom test fluid onto a Schwarzschild black hole will induce the mass of the black hole to decrease, however the backreaction was ignored in their...
Probing the intrinsic shape and alignment of dark matter haloes using SDSS galaxy groups (2008)
Wang, Yougang, Yang, Xiaohu, Mo, H. J., Li, Cheng, Van Den Bosch, Frank C., Fan, Zuhui, ...
Probing the intrinsic shape and alignment of dark matter haloes using SDSS galaxy groups (2008)
Wang, Yougang, Yang, Xiaohu, Mo, H. J., Li, Cheng, Van Den Bosch, Frank C., Fan, Zuhui, ...
We study the three-dimensional and projected shapes of galaxy groups in the Sloan Digital Sky Survey Data Release 4, and examine the alignment between the orientation of the central galaxy and the...
A Holographic Dark Energy Model from Ricci Scalar Curvature (2007)
Gao, Changjun, Wu, Fengquan, Chen, Xuelei, Shen, You-Gen
Motivated by the holographic principle, it has been suggested that the dark energy density may be inversely proportional to the area of the event horizon of the Universe. However, such a model would...
The Electron-Screening Correction for the Proton-Proton Reaction (2007)
John Bahcall, Xuelei Chen, Marc Kamionkowski
We test the Salpeter formalism for calculating electron screening of nuclear fusion reactions by solving numerically the relevant Schrodinger equation for the fundamental proton-proton reaction. We...
Features of holographic dark energy under the combined cosmological constraints (2007)
Ma, Yin-Zhe, Gong, Yan, Chen, Xuelei
We investigate the observational signatures of the holographic dark energy models in this paper, including both the original model and a model with an interaction term between the dark energy and...
Probing the Intrinsic Shape and Alignment of Dark Matter Haloes using SDSS Galaxy Groups (2007)
Wang, Yougang, Yang, Xiaohu, Mo, H. J., Li, Cheng, Fan, Zuhui, ...
We study the three-dimensional and projected shapes of galaxy groups in the Sloan Digital Sky Survey Data Release 4, and examine the alignment between the orientation of the central galaxy and the...
Type Ia supernovae as speed sensors at intermediate redshifts (2007)
The application of large scale peculiar velocity (LSPV), as a crucial probe of dark matter, dark energy and gravity, is severely limited by measurement obstacles. We show that fluctuations in type Ia...
Constraints on radiative dark-matter decay from the cosmic microwave background (2007)
Zhang, Le, Chen, Xuelei, Kamionkowski, Marc, Si, Zong-guo, Zheng, Zheng
If dark matter decays to electromagnetically interacting particles, it can inject energy into the baryonic gas and thus affect the processes of recombination and reionization. This leaves an imprint...
Two Component Model of Dark Energy (2007)
We consider the possibility that the dark energy is made up of two or more independent components, each having a different equation of state. We fit the model with supernova and gamma-ray burst (GRB)...
Contraints on radiative dark-matter decay from the cosmic microwave background (2007)
Zhang, Le, Chen, Xuelei, Kamionkowski, Marc, Si, Zongguo, Zheng, Zheng
If dark matter decays to electromagnetically-interacting particles, it can inject energy into the baryonic gas and thus affect the processes of recombination and reionization. This leaves an imprint...
Detecting First Star Lyman-$\alpha$ Spheres through Gravitational Telescopes (2007)
Li, Guoliang, Zhang, Pengjie, Chen, Xuelei
Lyman-$\alpha$ spheres, i.e. regions around the first stars which are illuminated by Lyman-$\alpha$ photons and show 21cm absorption feature against the CMB, are smoking guns at the dawn of the...
The 21cm Signature of the First Stars (2006)
Chen, Xuelei, Miralda-Escude, Jordi
We predict the 21-cm signature of the first metal-free stars. The soft X-rays emitted by these stars penetrate the atomic medium around their host halos, generating Lyman alpha photons that couple...
Zhang, Le, Chen, Xuelei, Lei, Yi-An, Si, Zongguo
The recombination history of the Universe provides a useful tool for constraining the annihilation of dark matter particles. Even a small fraction of dark matter particles annihilated during the...
Searching for CPT Violation with Cosmic Microwave Background Data from WMAP and BOOMERANG (2006)
Feng, Bo, Li, Mingzhe, Xia, Jun-Qing, Chen, Xuelei, Zhang, Xinmin
We search for signatures of Lorentz and $CPT$ violations in the cosmic microwave background (CMB) temperature and polarization anisotropies by using the WMAP and the 2003 flight of BOOMERANG (B03)...
Angular power spectrum of the galactic synchrotron radiation (2004)
We calculate the angular power spectrum of the galactic synchrotron radiation induced by the small scale fluctuations of the magnetic field and the cosmic ray electron density. Using the observed...
Particle decays during the cosmic dark ages (2004)
Chen, Xuelei, Kamionkowski, Marc
We consider particle decays during the cosmic dark ages with two aims: (1) to explain the high optical depth reported by the Wilkinson Microwave Anisotropy Probe (WMAP), and (2) to provide new...
Testing non-standard cosmological models with supernovae (2004)
In this work we study the magnitude-redshift relation of a non-standard cosmological model. The model under consideration was firstly investigated within a special case of metric-affine gravity (MAG)...
Particle decays during the cosmic dark ages (2003)
Chen, Xuelei, Kamionkowski, Marc
We consider particle decays during the cosmic dark ages with two aims: (1) to explain the high optical depth reported by WMAP, and (2) to provide new constraints to the parameter space for decaying...
Can Non-Gaussian Cosmological Models Explain the WMAP's High Optical Depth for Reionization? (2003)
Chen, Xuelei, Cooray, Asantha, Yoshida, Naoki, Sugiyama, Naoshi
The first-year Wilkinson Microwave Anisotropy Probe data suggest a high optical depth for Thomson scattering of 0.17 +/- 0.04, implying that the universe was reionized at an early epoch, z ~ 20. Such...
Chen, Xuelei, Miralda-Escude, Jordi
We investigate the interaction of Lyman alpha photons produced by the first stars in the universe with the intergalactic medium (IGM) prior to reionization. The background Lyman alpha spectral...
Thesis (Ph. D.)--University of Oklahoma, 2003.
X-ray Observations of the Warm-Hot Intergalactic Medium (2002)
Mathur, Smita, Weinberg, David H., Chen, Xuelei
We present Chandra observations that provide the most direct evidence to date for the pervasive, moderate density, shock-heated intergalactic medium predicted by leading cosmological scenarios. We...
Detecting the Baryons in Matter Power Spectra (2002)
Miller, Christopher J., Nichol, Robert C., Chen, Xuelei
We examine power spectra from the Abell/ACO rich cluster survey and the 2dF Galaxy Redshift Survey (2dfGRS) for observational evidence of features produced by the baryons. A non-negligible baryon...
Corrective lenses for high redshift supernovae (2002)
Dalal, Neal, Holz, Daniel E., Chen, Xuelei, Frieman, Joshua A.
Weak lensing of high-redshift Type Ia supernovae induces an external dispersion in their observed standard candle brightnesses, comparable in magnitude to the intrinsic dispersion for redshifts z>1....
Mathur, Smita, Weinberg, David, Chen, Xuelei
We present a high resolution (R~500) X-ray spectrum of the bright quasar H1821+643 (z=0.297), obtained in a 470 ksec Chandra observation. We search for X-ray absorption by highly ionized metal...
Chen, Xuelei, Weinberg, David H., Katz, Neal, Dave', Romeel
Using a hydrodynamic simulation of a LCDM universe, we investigate the "X-ray forest" absorption imprinted on the spectra of background quasars by the intervening intergalactic medium (IGM). In...
Chen, Xuelei, Hannestad, Steen, Scherrer, Robert J.
We study the effect on the cosmic microwave background (CMB) anisotropy and large scale structure (LSS) power spectrum of a scattering interaction between cold dark matter and baryons. This...
Kinetic Sunyaev-Zel'dovich effect from halo rotation (2001)
We discuss the kinetic Sunyaev-Zel'dovich (SZ) contribution to cosmic microwave background (CMB) temperature fluctuations due to coherent rotational velocity component of electrons within halos. This...
Kinetic decoupling of neutralino dark matter (2001)
Chen, Xuelei, Kamionkowski, Marc, Zhang, Xinmin
After neutralinos cease annihilating in the early Universe, they may still scatter elastically from other particles in the primordial plasma. At some point in time, however, they will eventually stop...
Kinetic decoupling of neutralino dark matter (2001)
Chen, Xuelei, Kamionkowski, Marc, Zhang, Xinmin
After neutralinos cease annihilating in the early Universe, they may still scatter elastically from other particles in the primordial plasma. At some point in time, however, they will eventually stop...
Extended quintessence and the primordial helium abundance (2000)
Chen, Xuelei, Scherrer, Robert J., Steigman, Gary
In extended quintessence models, a scalar field which couples to the curvature scalar R provides most of the energy density of the universe. We point out that such models can also lead naturally to a...
How to get less helium and more neutrinos from BBN (2000)
We discuss BBN in the presence of a non-minimally coupled quintessence model. In some of these models, the gravitational constant and cosmic expansion rate are smaller than standard model predicts....
The Helium abundance problem and non-minimally coupled quintessence (2000)
There is a tension between observed Helium abundance and the prediction of the standard Big Bang Nucleosynthesis. We show that non-minimally quintessence model may help to reduce this tension between...
Cosmic microwave background temperature and polarization anisotropy in Brans-Dicke cosmology (1999)
Chen, Xuelei, Kamionkowski, Marc
We develop a formalism for calculating cosmic microwave background (CMB) temperature and polarization anisotropies in cosmological models with Brans-Dicke gravity. We then modify publicly available...
Cosmic Microwave Background Temperature and Polarization Anisotropy in Brans-Dicke Cosmology (1999)
Chen, Xuelei, Kamionkowski, Marc
We develop a formalism for calculating cosmic microwave background (CMB) temperature and polarization anisotropies in cosmological models with Brans-Dicke gravity. We then modify publicly available...
Indirect Detection of Neutralino Annihilation from Three-body Channels (1999)
Chen, Xuelei, Kamionkowski, Marc
Three-body final states are included in the calculation of cross section and neutrino production in neutralino annihilations. In some regions of the parameter space, three-body channels maybe...
In this dissertation I investigate several topics in particle astrophysics and cosmology. In Chapter 1, we re-derive Salpeter's formalism for calculating the electron screening enhancement of nuclear...
Three-body annihilation of neutralinos below two-body thresholds (1998)
Chen, Xuelei, Kamionkowski, Marc
We calculate the cross section for s-wave neutralino annihilation to three-body final states below the W+W- and tbar t thresholds. Such three-body channels may dominate the annihilation cross section...
Three-Body Annihilation of Neutralinos Below Two-Body Thresholds (1998)
Chen, Xuelei, Kamionkowski, Marc
We calculate the cross section for s-wave neutralino annihilation to three-body final states below the W^+ W^- and t-bar t thresholds. Such three-body channels may dominate the annihilation cross...
Electron-screening correction for the proton-proton reaction (1998)
Bahcall, John N., Chen, Xuelei, Kamionkowski, Marc
We test the Salpeter formalism for the electron screening of the solar proton-proton fusion reaction by solving numerically the relevant Schrödinger equation. We evaluate exactly the square of the...
Instability of the one-texture universe (1997)
Chen, Xuelei, Hindmarsh, Mark, Kamionkowski, Marc, Liddle, Andrew R.
The one-texture universe, introduced by Davis in 1987, is a homogeneous mapping of a scalar field with an S^3 vacuum into a closed universe. It has long been known to mathematicians that such...
On the instability of the one-texture universe (1997)
Chen, Xuelei, Hindmarsh, Mark, Kamionkowski, Marc, Liddle, Andrew R
The one-texture universe, introduced by Davis in 1987, is a homogeneous mapping of a scalar field with an $S^3$ vacuum into a closed universe. It has long been known to mathematicians that such...
The Electron-Screening Correction for the Proton-Proton Reaction (1996)
Bahcall, John N., Chen, Xuelei, Kamionkowski, Marc
We test the Salpeter formalism for the electron screening of the solar proton-proton fusion reaction by solving numerically the relevant Schrodinger equation. We evaluate exactly the square of the...