3,577 research outputs found
Electromagnetic counterparts of high-frequency gravitational waves having additional polarization states: distinguishing and probing tensor-mode, vector-mode and scalar-mode gravitons
GWs from extra dimensions, very early universe, and some high-energy
astrophysical process, might have at most six polarizations: plus- and
cross-type (tensor-mode gravitons), x-, y-type (vector-mode), and b-, l-type
(scalar-mode). Peak or partial peak regions of some of such GWs are just
distributed in GHz or higher frequency band, which would be optimal band for
electromagnetic(EM) response. In this paper we investigate EM response to such
high-frequency GWs(HFGWs) having additional polarizations. For the first time
we address:(1)concrete forms of analytic solutions for perturbed EM fields
caused by HFGWs having all six possible polarizations in background stable EM
fields; (2)perturbed EM signals of HFGWs with additional polarizations in
three-dimensional-synchro-resonance-system(3DSR system) and in
galactic-extragalactic background EM fields. These perturbative EM fields are
actually EM counterparts of HFGWs, and such results provide a novel way to
simultaneously distinguish and display all possible six polarizations. It is
also shown: (i)In EM response, pure cross-, x-type and pure y-type
polarizations can independently generate perturbative photon fluxes(PPFs,
signals), while plus-, b- and l-type polarizations produce PPFs in different
combination states. (ii) All such six polarizations have separability and
detectability. (iii)In EM response to HFGWs from extra-dimensions,
distinguishing and displaying different polarizations would be quite possible
due to their very high frequencies, large energy densities and special
properties of spectrum. (iv)Detection band(10^8 to 10^12 Hz or higher) of PPFs
by 3DSR and observation range(7*10^7 to 3*10^9 Hz) of PPFs by FAST
(Five-hundred-meter-Aperture-Spherical Telescope, China), have a certain
overlapping property, so their coincidence experiments will have high
complementarity.Comment: 27 pages, 16 figure
AMG: Automated Efficient Approximate Multiplier Generator for FPGAs via Bayesian Optimization
Approximate computing is a promising approach to reduce the power, delay, and
area in hardware design for many error-resilient applications such as machine
learning (ML) and digital signal processing (DSP) systems, in which multipliers
usually are key arithmetic units. Due to the underlying architectural
differences between ASICs and FPGAs, existing ASIC-based approximate
multipliers do not offer symmetrical gains when they are implemented by FPGA
resources. In this paper, we propose AMG, an open-source automated approximate
multiplier generator for FPGAs driven by Bayesian optimization (BO) with
parallel evaluation. The proposed method simplifies the exact half adders (HAs)
for the initial partial product (PP) compression in a multiplier while
preserving coarse-grained additions for the following accumulation. The
generated multipliers can be effectively mapped to lookup tables (LUTs) and
carry chains provided by modern FPGAs, reducing hardware costs with acceptable
errors. Compared with 1167 multipliers from previous works, our generated
multipliers can form a Pareto front with 28.70%-38.47% improvements in terms of
the product of hardware cost and error on average. All source codes, reproduced
multipliers, and our generated multipliers are available at
https://github.com/phyzhenli/AMG.Comment: 7 pages, 2023 IEEE International Conference on Field-Programmable
Technology (ICFPT
The dynamics of a delayed generalized fractional-order biological networks with predation behavior and material cycle
In this paper, a delayed generalized fractional-order biological networks with predation behavior and material cycle is comprehensively discussed. Some criteria of stability and bifurcation for the present system is presented. Moreover some results of two delays are obtained. Finally, some numerical simulations are presented to support the analytical results
Distinguishing thermal histories of dark matter from structure formation
It is important to understand the implications of current observational
constraints and potential signatures on the thermal history of dark matter. In
this paper, we build the connection between the present-day velocities and the
production mechanism of dark matter and find that the current observation on
structure formation can be imposed to constrain the decoupling temperatures and
the phase-space distribution of dark matter. We further explore the potential
of distinguishing different possible thermal histories of dark matter with
hypothetical future observational data. Using the freeze-in/-out scenarios as
templates, we find that future precision data may uniquely identify the allowed
parameter spaces for freeze-in and freeze-out, or even completely rule out one
of the scenarios. This method can be more generally applied to other scenarios.Comment: 49 pages, 13 figures, 1 tabl
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