Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
120,869
result(s) for
"Wave physics"
Sort by:
Physics of highly multimode nonlinear optical systems
Linear multimode optical systems have enabled clean experimental observations and the applications of numerous phenomena that continually extend the boundaries of wave physics. The infrastructure that has enabled these studies facilitates the study of an even richer world of nonlinear multimode optical systems. Multimode nonlinear optical physics is full of emergent phenomena, including robust spatial attractors, multimode wave instabilities, and conservative and dissipative multimode solitons. Many of these effects push the limits of existing theoretical techniques, demanding new insights and approaches that could emerge from other fields, such as statistical mechanics, physics-informed machine learning, network science and beyond. Here we provide an overview of recent investigations of wave propagation in highly multimode nonlinear systems, principally multimode fibre waveguides and laser cavities. These systems, with their multifaceted control, low cost, scalability and ultrahigh bandwidth, are ideal physical platforms for exploring—and ultimately applying—high-dimensional nonlinear physics, from orderly but elusive objects like spatiotemporal solitons to dynamical complexity itself, both near and far from equilibrium.
Nonlinearities allow the large number of modes in a multimode fibre to interact and create emergent phenomena. This Review presents the breadth of the high-dimensional nonlinear physics that can be studied in this platform.
Journal Article
Compton black-hole scattering for s ≤ 5/2
A
bstract
Quantum scattering amplitudes for massive matter have received new attention in connection to classical calculations relevant to gravitational-wave physics. Amplitude methods and insights are now employed for precision computations of observables needed for describing the gravitational dynamics of bound massive objects such as black holes. An important direction is the inclusion of spin effects needed to accurately describe rotating (Kerr) black holes. Higher-spin amplitudes introduced by Arkani-Hamed, Huang and Huang at three points have by now a firm connection to the effective description of Kerr black-hole physics. The corresponding Compton higher-spin amplitudes remain however an elusive open problem. Here we draw from results of the higher-spin literature and show that physical insights can be used to uniquely fix the Compton amplitudes up to spin 5
/
2, by imposing a constraint on a three-point higher-spin current that is a necessary condition for the existence of an underlying unitary theory. We give the unique effective Lagrangians up to spin 5
/
2, and show that they reproduce the previously-known amplitudes. For the multi-graviton amplitudes analogous to the Compton amplitude, no further corrections to our Lagrangians are expected, and hence such amplitudes are uniquely predicted. As an essential tool, we introduce a modified version of the massive spinor-helicity formalism which allows us to conveniently obtain higher-spin states, propagators and compact expressions for the amplitudes.
Journal Article
Non-reciprocal interband Brillouin modulation
Non-reciprocal light propagation is essential to control optical crosstalk and back-scatter in photonic systems. However, realizing high-fidelity non-reciprocity in low-loss integrated photonic circuits remains challenging. Here, we experimentally demonstrate a form of non-local acousto-optic light scattering to produce non-reciprocal single-sideband modulation and mode conversion in an integrated silicon photonic platform. In this system, a travelling-wave acoustic phonon driven by optical forces in a silicon waveguide spatiotemporally modulates light in a separate waveguide through linear interband Brillouin scattering. This process extends narrowband optomechanics-based schemes for non-reciprocity to travelling-wave physics, enabling large operation bandwidths of more than 125 GHz and up to 38 dB of non-reciprocal contrast between forward- and backward-propagating optical waves. The modulator operation wavelength is tunable over a 35-nm range by varying the optical drive wavelength. Such travelling-wave acousto-optic interactions provide a promising path toward the realization of broadband, low-loss isolators and circulators within integrated photonics.
Journal Article
Statistical analysis of mirror mode waves in sheath regions driven by interplanetary coronal mass ejection
We present a comprehensive statistical analysis of mirror mode waves and the properties of their plasma surroundings in sheath regions driven by interplanetary coronal mass ejection (ICME). We have constructed a semi-automated method to identify mirror modes from the magnetic field data. We analyze 91 ICME sheath regions from January 1997 to April 2015 using data from the Wind spacecraft. The results imply that similarly to planetary magnetosheaths, mirror modes are also common structures in ICME sheaths. However, they occur almost exclusively as dip-like structures and in mirror stable plasma. We observe mirror modes throughout the sheath, from the bow shock to the ICME leading edge, but their amplitudes are largest closest to the shock. We also find that the shock strength (measured by Alfvén Mach number) is the most important parameter in controlling the occurrence of mirror modes. Our findings suggest that in ICME sheaths the dominant source of free energy for mirror mode generation is the shock compression. We also suggest that mirror modes that are found deeper in the sheath are remnants from earlier times of the sheath evolution, generated also in the vicinity of the shock. Keywords. Interplanetary physics (plasma waves and turbulence; solar wind plasma) – space plasma physics (waves and instabilities)
Journal Article
Revisiting a family of wormholes: geometry, matter, scalar quasinormal modes and echoes
We revisit a family of ultra-static Lorentzian wormholes which includes Ellis–Bronnikov spacetime as a special case. We first show how the required total matter stress energy (which violates the local energy conditions) may be split into a part due to a phantom scalar and another extra piece (which vanishes for Ellis–Bronnikov) satisfying the Averaged Null Energy Condition (ANEC) along radial null geodesics. Thereafter, we examine the effective potential for scalar wave propagation in a general setting. Conditions on the metric function, for which the effective potential may have double barrier features are written down and illustrated (using this class of wormholes). Subsequently, using numerous methods, we obtain the scalar quasinormal modes (QNMs). We note the behaviour of the QNMs as a function of
n
(the metric parameter) and
b
0
(the wormhole throat radius). Thus, the shapes and sizes of the wormholes, governed by the metric parameter
n
and the throat radius
b
0
are linked to the variation and the values of the QNMs. Finally, we demonstrate how, for large
n
, the time domain profiles exhibit, expectedly, the occurence of echoes. In summary, our results suggest that this family of wormholes may indeed be used as a template for further studies on the gravitational wave physics of exotic compact objects.
Journal Article
Observation of PT-symmetric quantum interference
A common wisdom in quantum mechanics is that the Hamiltonian has to be Hermitian in order to ensure a real eigenvalue spectrum. Yet, parity–time (PT)-symmetric Hamiltonians are sufficient for real eigenvalues and therefore constitute a complex extension of quantum mechanics beyond the constraints of Hermiticity. However, as only single-particle or classical wave physics has been exploited so far, an experimental demonstration of the true quantum nature of PT symmetry has been elusive. In our work, we demonstrate two-particle quantum interference in a PT-symmetric system. We employ integrated photonic waveguides to reveal that the quantum dynamics of indistinguishable photons shows strongly counterintuitive features. To substantiate our experimental data, we analytically solve the quantum master equation using Lie algebra methods. The ideas and results presented here pave the way for non-local PT-symmetric quantum mechanics as a novel building block for future quantum devices.
Journal Article
The origins of massive black holes
Massive black holes (MBHs) inhabit galactic centres, and power luminous quasars and active galactic nuclei, shaping their cosmic environment with the energy they produce. The origins of MBHs remain a mystery, and the recent detection by LIGO/Virgo of a black hole of almost 150 solar masses has revitalized the questions of whether there is a continuum between ‘stellar’ and ‘massive’ black holes, and what the seeds of MBHs are. Seeds could have formed in the first galaxies or could be related to the collapse of horizon-sized regions in the early Universe. Understanding the origins of MBHs straddles fundamental physics, cosmology and astrophysics, and bridges the fields of gravitational-wave physics and traditional astronomy. With several existing and upcoming facilities in the next 10–15 years, we foresee the possibility of discovering the avenues of formation of MBHs. This Review links three main topics: the channels of black hole seed formation, the journey from seeds to MBHs, and the diagnostics on the origins of MBHs. We highlight and critically discuss current unsolved problems, touching on recent developments.Massive black holes dwell in many galaxies, and various physical processes have been invoked to explain their presence. This Review discusses their formation channels, how they have grown over time from smaller seeds and how we can constrain their origins.
Journal Article
The Gravitational-wave physics II: Progress
It has been a half-decade since the first direct detection of gravitational waves, which signifies the coming of the era of the gravitational-wave astronomy and gravitational-wave cosmology. The increasing number of the detected gravitational-wave events has revealed the promising capability of constraining various aspects of cosmology, astronomy, and gravity. Due to the limited space in this review article, we will briefly summarize the recent progress over the past five years, but with a special focus on some of our own work for the Key Project “Physics associated with the gravitational waves” supported by the National Natural Science Foundation of China. In particular, (1) we have presented the mechanism of the gravitational-wave production during some physical processes of the early Universe, such as inflation, preheating and phase transition, and the cosmological implications of gravitational-wave measurements; (2) we have put constraints on the neutron star maximum mass according to GW170817 observations; (3) we have developed a numerical relativity algorithm based on the finite element method and a waveform model for the binary black hole coalescence along an eccentric orbit.
Journal Article
Gravitational-wave physics and astronomy in the 2020s and 2030s
The 100 years since the publication of Albert Einstein’s theory of general relativity saw significant development of the understanding of the theory, the identification of potential astrophysical sources of sufficiently strong gravitational waves and development of key technologies for gravitational-wave detectors. In 2015, the first gravitational-wave signals were detected by the two US Advanced LIGO instruments. In 2017, Advanced LIGO and the European Advanced Virgo detectors pinpointed a binary neutron star coalescence that was also seen across the electromagnetic spectrum. The field of gravitational-wave astronomy is just starting, and this Roadmap of future developments surveys the potential for growth in bandwidth and sensitivity of future gravitational-wave detectors, and discusses the science results anticipated to come from upcoming instruments.In the past few years, gravitational-wave observations provided stunning insights into some of the most cataclysmic events in the Universe, heralding a bright future for gravitational-wave physics and astronomy. This is a Roadmap for the field in the coming two decades.
Journal Article