17,318 research outputs found
Relativistic Astronomy. III. Test of Special Relativity via Doppler Effect
The Breakthrough Starshot program is planning to send transrelativistic probes to travel to nearby stellar systems within decades. Because the probe velocity is designed to be a good fraction of the light speed, Zhang & Li recently proposed that these transrelativistic probes can be used to study astronomical objects and to test special relativity. In this work, we propose some methods to test special relativity and constrain photon mass using the Doppler effect with the images and spectral features of astronomical objects as observed in the transrelativistic probes. We introduce more general theories to set up the framework of testing special relativity, including the parametric general Doppler effect and the Doppler effect with massive photons. We find that by comparing the spectra of a certain astronomical object, one can test Lorentz invariance and constrain photon mass. Additionally, using the imaging and spectrograph capabilities of transrelativistic probes, one can test time dilation and constrain photon mass. For a transrelativistic probe with velocity v ~ 0.2c, aperture D ~ 3.5 cm, and spectral resolution R ~ 100 (or 1000), we find that the probe velocity uncertainty can be constrained to σ v ~ 0.01c (or 0.001c), and the time dilation factor uncertainty can be constrained to (or 0.001), where is the time dilation factor and γ is the Lorentz factor. Meanwhile, the photon mass limit is set to m γ 10−33 g, which is slightly lower than the energy of the optical photon
Multiagent Bidirectionally-Coordinated Nets: Emergence of Human-level Coordination in Learning to Play StarCraft Combat Games
Many artificial intelligence (AI) applications often require multiple
intelligent agents to work in a collaborative effort. Efficient learning for
intra-agent communication and coordination is an indispensable step towards
general AI. In this paper, we take StarCraft combat game as a case study, where
the task is to coordinate multiple agents as a team to defeat their enemies. To
maintain a scalable yet effective communication protocol, we introduce a
Multiagent Bidirectionally-Coordinated Network (BiCNet ['bIknet]) with a
vectorised extension of actor-critic formulation. We show that BiCNet can
handle different types of combats with arbitrary numbers of AI agents for both
sides. Our analysis demonstrates that without any supervisions such as human
demonstrations or labelled data, BiCNet could learn various types of advanced
coordination strategies that have been commonly used by experienced game
players. In our experiments, we evaluate our approach against multiple
baselines under different scenarios; it shows state-of-the-art performance, and
possesses potential values for large-scale real-world applications.Comment: 10 pages, 10 figures. Previously as title: "Multiagent
Bidirectionally-Coordinated Nets for Learning to Play StarCraft Combat
Games", Mar 201
Higgs self-coupling in the MSSM and NMSSM after the LHC Run 1
Measuring the Higgs self-coupling is one of the crucial physics goals at the
LHC Run-2 and other future colliders. In this work, we attempt to figure out
the size of SUSY effects on the trilinear self-coupling of the 125 GeV Higgs
boson in the MSSM and NMSSM after the LHC Run-1. Taking account of current
experimental constraints, such as the Higgs data, flavor constraints,
electroweak precision observables and dark matter detections, we obtain the
observations: (1) In the MSSM, the ratio of
has been tightly constrained by the LHC
data, which can be only slightly smaller than 1 and minimally reach 97\%; (2)
In the NMSSM with , a sizable reduction of
can occur and minimally reach 10\%
when the lightest CP-even Higgs boson mass is close to the SM-like
Higgs boson due to the large mixing angle between the singlet and
doublet Higgs bosons; (3) In the NMSSM with , a large enhancement
or reduction can occur,
which is accompanied by a sizable change of coupling. The
future colliders, such as the HL-LHC and ILC, will have the capacity to test
these large deviations in the NMSSM.Comment: 28 pages, discussions and references added, matched to journal
versio
Long Term Spectral Evolution of Tidal Disruption Candidates Selected by Strong Coronal Lines
We present results of follow-up optical spectroscopic observations of seven
rare, extreme coronal line emitting galaxies reported by Wang et al. (2012)
with Multi-Mirror Telescope (MMT). Large variations in coronal lines are found
in four objects, making them strong candidates of tidal disruption events
(TDE). For the four TDE candidates, all the coronal lines with ionization
status higher than [Fe VII] disappear within 5-9 years. The [Fe VII] faded by a
factor of about five in one object (J0952+2143) within 4 years, whereas emerged
in other two without them previously. A strong increment in the [O III] flux is
observed, shifting the line ratios towards the loci of active galactic nucleus
on the BPT diagrams. Surprisingly, we detect a non-canonical [O III]5007/[O
III]4959 2 in two objects, indicating a large column density of O and
thus probably optical thick gas. This also requires a very large ionization
parameter and relatively soft ionizing spectral energy distribution (e.g.
blackbody with K). Our observations can be explained as
echoing of a strong ultraviolet to soft X-ray flare caused by tidal disruption
events, on molecular clouds in the inner parsecs of the galactic nuclei.
Re-analyzing the SDSS spectra reveals double-peaked or strongly blue-shouldered
broad lines in three of the objects, which disappeared in the MMT spectra in
two objects, and faded by a factor of ten in 8 years in the remaining object
with a decrease in both the line width and centroid offset. We interpret these
broad lines as arising from decelerating biconical outflows. Our results
demonstrate that the signatures of echoing can persist for as long as ten
years, and can be used to probe the gas environment in the quiescent galactic
nuclei.Comment: 30 Pages, 10 Figures, 2 Tables, Accepted for Publication in Ap
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