High-frequency gravitational waves having large spectral densities and their electromagnetic response
Fang-Yu Li · Hao Wen · Zhen-Yun Fang
Abstract and summary · read the original at the source
In one page
A gravitational wave crossing a strong magnetic field turns partly into light. That is the inverse Gertsenshtein effect, and Li Fang-Yu, Wen Hao and Fang Zhen-Yun of Chongqing University take it as the starting point for a detector. Their target is the high-frequency end of the spectrum — a hundred megahertz up to a terahertz — where relic waves from the early universe, oscillating branes, plasma driven by intense radiation and even collider events are all expected to leave something, and where the big interferometers simply do not listen. The team works through five schemes and prices each one: the bare conversion effect, the same effect helped by a coherent radio beam, a flat superconducting cavity, a closed cylindrical superconducting cavity, and their own synchro-resonance system, in which a Gaussian microwave beam meets the wave inside a nine-tesla field. Their conclusion is that the last of these can in principle reach amplitudes near ten to the minus thirty-two, and that what stands in the way is engineering rather than physics.
Why it matters hereChapter 10 rests on electromagnetism and gravity being two sides of one coupling, and the Gertsenshtein effect is that coupling written down as a published, calculable, two-way conversion: field into wave, wave into field. Chapter 11 gets the hardware — superconducting cavities with quality factors in the hundreds of billions, used as gravitational antennas — and chapter 4 gets the reminder that a metric disturbance is something you can build an instrument for. Read it beside the same group’s signal-photon-flux calculation at /library/stm-c15757c634, Beckwith and Robertson on relic high-frequency waves at /library/stm-c1ad7838f6, and the international review of megahertz-to-gigahertz searches at /library/stm-96e41ddb23.
What it claims
01The Gertsenshtein effect and its inverse follow from the Einstein-Maxwell equations: an electromagnetic wave crossing a transverse static magnetic field generates gravitational waves, and a gravitational wave crossing the same field generates an electromagnetic wave — and for a laboratory-sized interaction region the relevant band is roughly 10⁸ Hz to 10¹² Hz.Section 2.1; Eq. 1
Settled physics02The signal photon flux from the inverse Gertsenshtein effect grows in proportion to the gravitational-wave frequency, so a high-frequency graviton has a larger interaction cross-section with a static magnetic field than a low-frequency one, and the minimal detectable amplitude falls as the inverse of the frequency, of the field strength, of the interaction length and of the square root of the receiving area.Section 2.1; Eqs. 3 and 4
Published and peer-reviewed03With a detectable minimum power of about 10⁻²² W in a 1 Hz bandwidth, a 9 T field, a 3 m interaction length and a 0.36 m² receiving surface, the bare inverse Gertsenshtein scheme reaches a minimal detectable amplitude of 1.8 times 10⁻²¹ at 3 GHz and 1.8 times 10⁻²⁴ at 3 THz — within reach of the brane-oscillation prediction of about 10⁻²², and far from the 10⁻²⁹ to 10⁻³⁰ expected of relic waves.Section 2.1; Eqs. 5; brane oscillation limit from ref. 11
Designed, not yet built04Adding a coherent plane electromagnetic wave lifts the signal to first order in the wave amplitude instead of second, a ratio of about 10¹¹ in photon flux for the worked parameters — but the background beam shares the signal’s direction and distribution, so after the noise is accounted for the sensitivity gain is only one to two orders of magnitude.Section 2.2; Eqs. 7 to 10; Figure 1
Published and peer-reviewed05Superconducting cavities do better on the same field: a planar open cavity of 0.05 m³ with quality factor 10⁷ at 9 T and 3 GHz reaches 3.9 times 10⁻²³ for a non-stochastic wave, and a closed cylindrical cavity of radius 0.35 m and length 89 cm with quality factor 10¹¹ reaches 3.0 times 10⁻²⁶ — with the caveat that cavity signal energy depends on the wave’s amplitude rather than its frequency.Sections 2.3 and 2.5; Eqs. 16 and 30; Concluding remark IV
Designed, not yet built06In the synchro-resonance system the perturbative photon flux is transverse and differs from the background beam in distribution, direction, polarisation and decay rate, so it can be separated by choosing the position and orientation of the receiving surface; with 9 T, a 10 W Gaussian beam, a 2 m interaction length, an operating temperature near 0.14 K and 10⁶ s of integration the scheme reaches about 5.7 times 10⁻³², and the authors argue the remaining barriers are engineering and technology rather than a limit of principle.Section 2.6; Eqs. 37 and 38; Figures 3 and 4; Section 3, points I to III and V
Designed, not yet built
Read it · abstract
Abstract
Various cosmology models, brane oscillation scenarios, interaction of interstellar plasma with intense electromagnetic radiation, and even high-energy physics experiments (e.g., Large Hadron Collider (LHC)) all predict high frequency gravitational waves (HFGWs, i.e., high-energy gravitons) in the microwave band and higher frequency region, and some of them have large energy densities. Electromagnetic (EM) detection to such HFGWs would be suitable due to very high frequencies and large energy densities of the HFGWs. We review several typical EM detection schemes, i.e., inverse Gertsenshtein effect (G-effect), coupling of the inverse G effect with a coherent EM wave, coupling of planar superconducting open cavity with a static magnetic field, cylindrical superconducting closed cavity, and the EM sychro-resonance system, and discuss related minimal detectable amplitudes and sensitivities. Furthermore, we give some new ideas and improvement ways enhancing the possibility of measuring the HFGWs. It is shown that there is still a large room for improvement for those schemes to approach and even reach up the requirement of detection of HFGWs expected by the cosmological models and high-energy astrophysical process.
Keywords high-frequency gravitational waves, electromagnetic response of high-frequency gravitational waves, superconducting microwave cavities, synchro-resonance system.
PACS numbers 04.30.Nk, 04.25.Nx, 04.30.Db, 04.80.Nn
(Abstract only — see the rights note above. The complete paper, with the five detection schemes worked through and their sensitivity figures, is free to read at the journal. On this site, the same Chongqing group’s calculation of signal photon flux and background noise in the coupling detector is at /library/stm-c15757c634, Andrew Beckwith and Glen Robertson on relic high-frequency waves from the Big Bang is at /library/stm-c1ad7838f6, and the international review of the challenges and opportunities of megahertz-to-gigahertz gravitational-wave searches is at /library/stm-96e41ddb23.)
The way in
https://doi.org/10.1088/1674-1056/22/12/120402Published as Chinese Physics B 22 (2013) 120402 by Li Fang-Yu, Wen Hao and Fang Zhen-Yun of the Department of Physics, Chongqing University; received 9 April 2013, revised 20 May 2013. The article page carries the line ‘© 2013 Chinese Physical Society and IOP Publishing Ltd’ and no Creative Commons statement appears in the text or on the journal’s article page, checked on 2026-09-08, so this sheet carries the summary, the claims and the authors’ own abstract and sends the reader to the source. The paper is not on arXiv under this title. The version read for these claims is the free author-copy PDF served by the journal at cpb.iphy.ac.cn for this DOI; the claims are located against its numbered sections, equations and figures. The work was supported by the National Natural Science Foundation of China (grants 11075224 and 11375279) and the Foundation of the China Academy of Engineering Physics (grants 2008 T0401 and T0402).
How to cite it
Fang-Yu Li, Hao Wen, Zhen-Yun Fang (2013) High-frequency gravitational waves having large spectral densities and their electromagnetic response. doi:10.1088/1674-1056/22/12/120402
Where it sits in the curriculum
Gravity control and superconductorsScalar waves and the field behind the fieldsThe metric, warp drives and wormholes