Article
Astronomy & Astrophysics
Anibal Faundez, Radouane Gannouji
Summary: We studied the existence and stability of Q-balls in noncanonical scalar field theories. We extended the Vakhitov-Kolokolov stability criterion to K-field theories and derived the condition for well-posed Cauchy problem of perturbations. We found that K,X > 0 and K,X + XK,XX > 0 are necessary but not sufficient conditions, and that perturbations define a strongly hyperbolic system if (K,X - 2002K,XX)(K,X + 2 omega 202K,X X) > 0. The noncanonical scalar field can lower the charge and energy of the Q-ball, improving its stability.
Article
Physics, Multidisciplinary
Daniel G. Figueroa, Joanes Lizarraga, Ander Urio, Jon Urrestilla
Summary: This study focuses on the nonlinear dynamics of axion inflation, highlighting the importance of considering inhomogeneity effects. The results reveal new insights into the behavior of axion inflation and have significant implications for its phenomenology and observability.
PHYSICAL REVIEW LETTERS
(2023)
Article
Astronomy & Astrophysics
Xinyi Zhang, Che-Yu Chen, Yakefu Reyimuaji
Summary: This paper proposes a modified gravity framework for inflation by adding a direct f (phi)T term, investigates inflation dynamics, applies it to three inflationary models, and finds that predictions are sensitive to this new term. This f (phi)T gravity brings chaotic and natural inflation into better agreement with data and allows a larger tensor-to-scalar ratio in the Starobinsky model.
Article
Astronomy & Astrophysics
Zeinab Teimoori, Kazem Rezazadeh, Kayoomars Karami
Summary: This study investigates the formation of primordial black holes (PBHs) as a possible candidate for dark matter, utilizing a gravitationally enhanced friction mechanism. By considering a nonminimal derivative coupling between the scalar field and gravity, three parameter sets were identified that resulted in ultra slow-roll inflation, leading to the formation of PBHs. The model also predicts the presence of secondary gravitational waves (GWs) at frequencies within the sensitivity region of certain GW detectors, allowing for observational compatibility assessment.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Mahmoud AlHallak, Khalil Kalid Al-Said, Nidal Chamoun, Moustafa Sayem El-Daher
Summary: We investigate natural inflation within the warm inflation paradigm, considering non-minimal coupling to gravity and both strong and weak dissipation limits. We show that for a T-linearly dependent dissipative term, it can accommodate the observables n(s) and r given by Planck 2018 constraints, but with a too-small e-folding number to solve the horizon problem. A T-cubically dependent dissipative term may provide a solution to this e-folding number issue.
Article
Astronomy & Astrophysics
Noriaki Kitazawa
Summary: In the realistic model of cosmic inflation, the inflaton potential should be flat and stable under quantum corrections. This study presents a general formulation of the idea of the inflaton as a Nambu-Goldstone boson of spontaneous breaking of symmetry. It investigates the generation mechanism of necessary thermal dissipation term in the inflaton field equation for warm inflation without large thermal corrections to the inflaton potential.
Article
Economics
Thomas M. Mertens, John C. Williams
Summary: This paper analyzes the effects of the lower bound for interest rates on the distributions of inflation and interest rates in a New Keynesian model. It finds that there are two equilibria with different policy constraints, and the lower bound has a sizable effect on the distribution of interest rates while its impact on inflation is relatively modest.
AMERICAN ECONOMIC REVIEW
(2021)
Article
Astronomy & Astrophysics
Mehdi Shokri, Jafar Sadeghi, Mohammad Reza Setare, Salvatore Capozziello
Summary: In this paper, a single-field inflationary model modified by a nonminimal coupling term is studied in the context of constant-roll inflation, using a first-order formalism. The approach considers two functions of the scalar field and can be applied to various cosmological situations, analyzing power-law and exponential couplings separately. The inflationary parameters of the models are compared with CMB observations to achieve a physically motivated model.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2021)
Article
Environmental Studies
Jingwei Han, Chandrashekar Raghutla, Krishna Reddy Chittedi, Zhixiong Tan, Mansoor Ahmed Koondhar
Summary: This study examines the impact of natural resources, economic growth, export diversity, and inflation on financial development in the top-10 natural resource abundant countries. The findings suggest a long-run equilibrium relationship among these factors, with export diversity, economic growth, and inflation positively affecting financial development, while natural resources have a negative impact. Furthermore, the study indicates a unidirectional causality from financial development to export diversity and inflation.
Article
Astronomy & Astrophysics
Alireza Talebian, Amin Nassiri-Rad, Hassan Firouzjahi
Summary: This paper revisits the axion inflation model in the context of stochastic inflation and studies the effects of stochastic noise associated with electromagnetic fields. It is found that one polarization of the gauge field is amplified due to the parity-violating interaction, resulting in a large curvature perturbation. By considering the stochastic kicks arising from short modes at horizon crossing, Langevin equations for the long modes of the electromagnetic and axion fields are obtained. The dynamics of the electromagnetic fields are shown to follow a mean-reverting process, balancing the tachyonic growth of the gauge fields with diffusion forces. As the instability parameter grows towards the end of inflation, the large curvature perturbations induced by gauge field perturbations lead to the production of a significant amount of small mass primordial black holes (PBHs). It is demonstrated that the produced PBHs follow Gaussian statistics. Imposing observational constraints on PBH formation relaxes previous bounds on the instability parameter by approximately fifty percent.
Article
Astronomy & Astrophysics
Fuminobu Takahashi, Wen Yin
Summary: The recent report emphasizes the presence of Hubble tension and explores the impact of various cosmological models on this issue. Some models may have a scalar spectral index greater than the predicted value by ACDM, and even allow for a scale-invariant scenario. Therefore, studying special early Universe models is crucial for understanding this unusual n(s).
Article
Environmental Studies
Ming Fang, Chiu-Lan Chang
Summary: The COVID-19 pandemic has had a significant impact on the global economy, including the energy market and sector. This study investigated the impact of oil and natural gas trading and globalization on natural resources management in China. The results showed positive linkages between oil and natural gas trading, globalization, economic growth, industrialization, inflation, and natural resources management in China. The study suggests that practitioners should focus on the need for globalization and human capital development to ensure effective natural resources management.
Article
Quantum Science & Technology
Alex May
Summary: Using the AdS/CFT correspondence, we investigate the constraint of gravity on computation. In this framework, computation with gravity in a bulk region is related to non-gravitational physics in the corresponding boundary region. Our study reveals that the complexity of local operations determines the amount of entanglement required for implementing non-local computations. Furthermore, the complexity and entanglement cost are found to have a polynomial relationship. Therefore, gravity constrains the complexity of operations within specific regions to be polynomial in the area of the corresponding surface.
Article
Multidisciplinary Sciences
Richard P. Woodard
Summary: In this article, some reminiscences of the late Steven Weinberg are shared. Then, a topic in quantum field theory is discussed, which is the role of state wave functionals in deriving the ie term of the Feynman propagator when using functional formalism. While it may be a curiosity for in-out scattering amplitudes on flat-space backgrounds, it holds much greater significance for the in-in amplitudes of the Schwinger-Keldysh formalism in cosmology. It also addresses Weinberg's wonder about the fate of large logarithms sometimes found in quantum corrections from inflationary particle production.
Article
Physics, Fluids & Plasmas
Jaroslaw Kwapien, Pawel Blasiak, Stanislaw Drozdz, Pawel Oswiecimka
Summary: Based on mathematical arguments within the MFDFA approach, this study shows that multifractality effects in uncorrelated time series from the Gaussian basin of attraction disappear asymptotically for positive moments as the length of the time series increases. The findings also suggest that this may apply to negative moments as well, extending to the Levy stable regime of fluctuations. Numerical simulations confirmed these effects, indicating that genuine multifractality in time series only results from long-range temporal correlations and fatter distribution tails. The presence of such correlations broadens the width of the singularity spectrum. The question of whether temporal correlations or broad distribution tails contribute to multifractality in time series is therefore ill posed. Without correlations, only bifractal or monofractal cases are possible, corresponding to fluctuations in the Levy stable regime or the Gaussian basin of attraction, respectively.
Article
Astronomy & Astrophysics
S. A. Levshakov, K-W Ng, C. Henkel, B. Mookerjea, I. I. Agafonova, S-Y Liu, W-H Wang
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2019)
Article
Astronomy & Astrophysics
Wei-Chih Huang, Kin-Wang Ng, Tzu-Chiang Yuan
Article
Physics, Particles & Fields
Po-Wen Chang, Cheng-Wei Chiang, Kin-Wang Ng
JOURNAL OF HIGH ENERGY PHYSICS
(2020)
Article
Astronomy & Astrophysics
Chun-Hung Chen, Hing-Tong Cho, Anna Chrysostomou, Alan S. Cornell
Summary: This research validates the connection between integer and half-integer spin perturbations using the monodromy technique and provides new results for the asymptotic quasinormal frequencies in different scenarios.
CLASSICAL AND QUANTUM GRAVITY
(2022)
Article
Astronomy & Astrophysics
Hing-Tong Cho, Jen-Tsung Hsiang, Bei-Lok Hu
Summary: This paper revisits the issue of the near-unity value of the ratio of fluctuations in the vacuum energy density of quantum fields to the mean. By calculating the heat capacity and quantum compressibility, the thermodynamic stability of quantum matter fields in different spacetimes is examined. The results provide qualitative observations on the compatibility condition for the co-existence between quantum fields and spacetimes.
Article
Astronomy & Astrophysics
Guo-Chin Liu, Kin-Wang Ng
Summary: The detection of gravitational waves from binary compact star mergers has opened a new era in astrophysics and cosmology. Current experiments are searching for a stochastic gravitational wave background by correlating signals from multiple detectors. In this work, a method based on spherical harmonic expansion is applied to calculate the overlap reduction functions for third-generation detectors.
Article
Astronomy & Astrophysics
Reginald Christian Bernardo, Kin-Wang Ng
Summary: Pulsar timing provides an independent way to test general relativity and alternative gravity theories. This work focuses on studying an isotropic stochastic gravitational wave background and presents a straightforward formalism for obtaining the power spectrum and the overlap reduction function in a pulsar timing array. The results pave the way for an efficient numerical method to examine the gravitational wave-induced spatial correlations across millisecond pulsars.
Article
Astronomy & Astrophysics
Guo-Chin Liu, Kin -Wang Ng
Summary: This study focuses on the observation of a stochastic gravitational-wave background (SGWB) made by a pulsar timing array in the spherical harmonic space. A fast algorithm is developed to compute the overlap reduction functions for the intensity and polarization anisotropies of SGWB. The study also calculates the bipolar spherical harmonic coefficients for characterizing the statistical isotropy of SGWB, with a specific focus on the linear polarization anisotropy.
Article
Astronomy & Astrophysics
Hing-Tong Cho, Bei-Lok Hu
Summary: This work investigates the effects of gravitons and their fluctuations on the dynamics of two masses using the Feynman-Vernon influence functional formalism. The study solves for the fluctuations of the masses' separation due to the graviton noise, considering various quantum states. The possibility of detecting these fluctuations in primordial gravitons using interferometers in deep space experiments is also discussed.
Article
Astronomy & Astrophysics
Yu-Kuang Chu, Guo-Chin Liu, Kin-Wang Ng
Summary: This study focuses on the interferometric observation of intensity and polarization anisotropies of a stochastic gravitational wave background. The observed correlated data is defined in the group manifold of the three-dimensional rotation. Explicit correlation between two detectors in interferometry experiments is constructed using the Wigner-D functions, which may be useful for estimating the power spectra of the stochastic gravitational wave background anisotropies.
Article
Astronomy & Astrophysics
Wei-Can Syu, Da-Shin Lee, Kin-Wang Ng
Article
Astronomy & Astrophysics
Chia-Min Lin, Kin-Wang Ng, Kingman Cheung
Article
Astronomy & Astrophysics
Shu-Lin Cheng, Wolung Lee, Kin-Wang Ng
