14,108 research outputs found
Quantum simulation of dark energy candidates
Additional scalar fields from scalar-tensor, modified gravity or higher
dimensional theories beyond general relativity may account for dark energy and
the accelerating expansion of the Universe. These theories have lead to
proposed models of screening mechanisms, such as chameleon and symmetron
fields, to account for the tight experimental bounds on fifth-force searches.
Cold atom systems have been very successfully used to constrain the parameters
of these screening models, and may in future eliminate the interesting
parameter space of some models entirely. In this paper, we show how to
manipulate a Bose-Einstein condensate to simulate the effect of any screened
scalar field model coupled conformally to the metric. We give explicit
expressions for the simulation of various common models. This result may be
useful for investigating the computationally challenging evolution of particles
on a screened scalar field background, as well as for testing the metrology
scheme of an upcoming detector proposal.Comment: 26 pages, 3 figure
Towards secure end-to-end data aggregation in AMI through delayed-integrity-verification
The integrity and authenticity of the energy usage data in Advanced Metering Infrastructure (AMI) is crucial to ensure the correct energy load to facilitate generation, distribution and customer billing. Any malicious tampering to the data must be detected immediately. This paper introduces secure end-to-end data aggregation for AMI, a security protocol that allows the concentrators to securely aggregate the data collected from the smart meters, while enabling the utility back-end that receives the aggregated data to verify the integrity and data originality. Compromise of concentrators can be detected. The aggregated data is protected using Chameleon Signatures and then forwarded to the utility back-end for verification, accounting, and analysis. Using the Trapdoor Chameleon Hash Function, the smart meters can periodically send an evidence to the utility back-end, by computing an alternative message and a random value (m', r) such that m' consists of all previous energy usage measurements of the smart meter in a specified period of time.
By verifying that the Chameleon Hash Value of (m', r) and that the energy usage matches those aggregated by the concentrators, the utility back-end is convinced of the integrity and authenticity of the data from the smart meters. Any data anomaly between smart meters and concentrators can be detected, thus indicating potential compromise of concentrators
Dark Energy vs. Modified Gravity
Understanding the reason for the observed accelerated expansion of the
Universe represents one of the fundamental open questions in physics. In
cosmology, a classification has emerged among physical models for the
acceleration, distinguishing between Dark Energy and Modified Gravity. In this
review, we give a brief overview of models in both categories as well as their
phenomenology and characteristic observable signatures in cosmology. We also
introduce a rigorous distinction between Dark Energy and Modified Gravity based
on the strong and weak equivalence principles.Comment: 29 pages, 4 figures; invited review submitted to Annual Reviews of
Nuclear and Particle Science; v2: some pertinent references added; v3: table
with constraints added, reflects published version; v4 [trivial]: fixed
missing references in arxiv versio
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