Monthly Notices of the Royal Astronomical Society, 2021
ABSTRACTObservations in the lowest Murchison Widefield Array (MWA) band between 75 and 100 MHz ha... more ABSTRACTObservations in the lowest Murchison Widefield Array (MWA) band between 75 and 100 MHz have the potential to constrain the distribution of neutral hydrogen in the intergalactic medium at redshift ∼13–17. Using 15 h of MWA data, we analyse systematics in this band such as radio-frequency interference (RFI), ionospheric and wide field effects. By updating the position of point sources, we mitigate the direction-independent calibration error due to ionospheric offsets. Our calibration strategy is optimized for the lowest frequency bands by reducing the number of direction-dependent calibrators and taking into account radio sources within a wider field of view. We remove data polluted by systematics based on the RFI occupancy and ionospheric conditions, finally selecting 5.5 h of the cleanest data. Using these data, we obtain 2σ upper limits on the 21 cm power spectrum in the range of $0.1~ h~{\mathrm{ Mpc}}^{-1}\lessapprox k \lessapprox 1 ~ ~h~{\mathrm{ Mpc}}^{-1}$ and at z = 1...
Monthly Notices of the Royal Astronomical Society, 2020
Cosmic strings are potential gravitational-wave (GW) sources that can be probed by pulsar timing ... more Cosmic strings are potential gravitational-wave (GW) sources that can be probed by pulsar timing arrays (PTAs). In this work we develop a detection algorithm for a GW burst from a cusp on a cosmic string, and apply it to Parkes PTA data. We find four events with a false alarm probability less than 1 per cent. However further investigation shows that all of these are likely to be spurious. As there are no convincing detections we place upper limits on the GW amplitude for different event durations. From these bounds we place limits on the cosmic string tension of Gμ ∼ 10−5, and highlight that this bound is independent from those obtained using other techniques. We discuss the physical implications of our results and the prospect of probing cosmic strings in the era of Square Kilometre Array.
Publications of the Astronomical Society of Australia, 2020
Gravitational waves from coalescing neutron stars encode information about nuclear matter at extr... more Gravitational waves from coalescing neutron stars encode information about nuclear matter at extreme densities, inaccessible by laboratory experiments. The late inspiral is influenced by the presence of tides, which depend on the neutron star equation of state. Neutron star mergers are expected to often produce rapidly rotating remnant neutron stars that emit gravitational waves. These will provide clues to the extremely hot post-merger environment. This signature of nuclear matter in gravitational waves contains most information in the 2–4 kHz frequency band, which is outside of the most sensitive band of current detectors. We present the design concept and science case for a Neutron Star Extreme Matter Observatory (NEMO): a gravitational-wave interferometer optimised to study nuclear physics with merging neutron stars. The concept uses high-circulating laser power, quantum squeezing, and a detector topology specifically designed to achieve the high-frequency sensitivity necessary ...
Volume: The Astronomical Society of the Pacific, ADASS XXV: The 25th Annual ADASS Conference 2017... more Volume: The Astronomical Society of the Pacific, ADASS XXV: The 25th Annual ADASS Conference 2017<br>
Optically levitated nanosensors in high vacuum are excellent candidates for the detection of high... more Optically levitated nanosensors in high vacuum are excellent candidates for the detection of high-frequency gravitational waves, amongst a wider range of other potential applications. We investigate the possibility of detecting high-frequency gravitational waves with levitated opto-mechanics. The current work proposes a laser-cooled optically-levitated nano-sensor to search for a number of highly-energetic sources associated with distant cosmic events, via precision sensing of gravitational waves at micron length scale.
14th Pacific Rim Conference on Lasers and Electro-Optics (CLEO PR 2020), 2020
We propose a small-scale spaceborne probe which uses laser-cooled optically-levitated nanoparticl... more We propose a small-scale spaceborne probe which uses laser-cooled optically-levitated nanoparticles to search for a variety of sources associated with high frequency cosmic events, through high-precision measurements and detection of gravitational waves at micron distances.
We aim to analyze the validity and consistency conditions as well as the generic predictions for ... more We aim to analyze the validity and consistency conditions as well as the generic predictions for string and superstring theory models in low energy physics context, covering a range of challenging ideas that are part of the field, from the Weak Gravity Conjecture, compactifications, string vacua, low-energy supersymmetry, gauge-symmetry breaking and supersymmetry breaking to heterotic strings, D-branes, M-Theory and large dimensions. We identify the theoretical implications, current concerns and experimental constraints of candidate string theories in the low energy limit, that are underlying certain solutions to several nontrivial problems such as the dimensionality of space-time, naturalness, supersymmetry and supergravity, axions and the strong CP problem, Yukawa couplings, black hole information paradox or grand unification. We finally discuss the effective field theory relevant for low energy precision physics at scales probed in table-top laboratory experiments and justify its...
14th Pacific Rim Conference on Lasers and Electro-Optics (CLEO PR 2020), 2020
We propose to extend the search for new physics beyond Standard Model using optically trapped and... more We propose to extend the search for new physics beyond Standard Model using optically trapped and laser cooled dielectric nanoparticles for the resonant detection of short-range forces and corrections to Newtonian gravity.
The aim of this unique monograph is to give a comprehensive review of the development of cosmolog... more The aim of this unique monograph is to give a comprehensive review of the development of cosmological inflation theory, scalar field cosmology, numerical results and simulations. The book provides ...
Classical Field Theory is a graduate level introduction to modern classical field theory, includi... more Classical Field Theory is a graduate level introduction to modern classical field theory, including electromagnetism and general relativity and describes various classical methods for fields with negligible quantum effects. The book is an expanded version of a field theory course in São Paulo. The author focuses on different theoretical solutions that require classical field theory methods, aiming to assist graduate students and researchers in easily make usage of classical field theory methods and adjust to this conceptual level before jumping directly into a course of quantum field theory. The book provides a theoretical framework for understanding fields and the methods associated with them. Most modern methods of classical field theory don’t get included into the standard student curriculum, making this book an invaluable asset. The book makes the transition between classical fields and quantum field theory much smoother and safe. The textbook provides a comprehensive review of classical mechanics, from Lagrangean, equations of motion to the Hamiltonian formalism, conservation laws, canonical transformations and the HamiltonJacobi theory. The author focuses on symmetries, groups, Lie algebras, Abelian Lie group invariance, cyclic groups and representations. The author also reviews the kinematics and dynamics of Special Relativity, Lorentz tensors, covariant Lagrangeans and the Lorentz group. The author defines the notion of field and introduces electromagnetism as a field theory, describing Maxwell’s equations and the EulerLagrange equations. The scalar field, its origins and applications are also present, together with their Lagrangeans, models and the equations of motion. Classical integrability, the continuum limit of discrete, lattice and spin systems are also provided. The book introduces us to the classical perturbation theory, polynomial potential and the formal solutions to the equations of motion. The book also covers the representations of the Lorentz group (Poincaré group, universal cover, Wigner method), rotation matrices, the spin-statistics theorem, Maxwell equation, Abelian vector fields, Proca field, energy-momentum tensor, Maxwell duality, electromagnetic waves and the motion of charged particles. The author describes Hofion solution and Hopf map, complex scalar fields and gauging global symmetries. The book introduces the reader also to the Noether theorem and its applications, nonrelativistic and relativistic fluid dynamics, including fluid vortices and knots. The second part of the book focuses on Solitons and topology as well as Non-Abelian theory (Kink solutions, Sine-Gordon, domain walls and topology, the Skyrmion scalar field, topological numbers, field theory solitons for condensed matter, XY and Rotor model, Spins, superconductivity, Landau-Ginzburg model and the Kosterlitz-Thouless phase transition. The radiation of classical scalar fields (Heisenberg model), Derrick’s theorem, symmetry breaking and the Abelian-Higgs system are also presented, together with the Non-Abelian gauge theory, Yang-Mills equation, Dirac monopole, Diract quantisation, the instanton, nontopological solutions, unstable solitons and moduli space. The last part of the book focuses on other spins or statistics, together with General relativity, from Chern-Simons theory, emergent gauge fields, Quantum Hall effect, Anyon statistics, massive theory, particle-vortex and particle-sting dualities, fermions andDirac spinors or the Dirac equation. The General relativity part contains concepts such as Einstein action and equation, perturbative and non-perturbative gravity, gravitational waves, time-dependent gravity and cosmology, gauges, dimensional reduction, cosmic strings, gravitational instantons and black hole solutions. Each chapter ends with further reading notes and several exercises, allowing the reader to identify the key aspects of the chapter and test their understanding.
Chern–Simons (Super)gravity is based on a suite of lecture notes on gravitational Chern–Simons th... more Chern–Simons (Super)gravity is based on a suite of lecture notes on gravitational Chern–Simons theories developed by two respected experts on general relativity and quantum field theory. Both the b...
one of ‘work in progress’. For this reviewer, some interesting questions can be raised. I wonder ... more one of ‘work in progress’. For this reviewer, some interesting questions can be raised. I wonder how we may ever know if such a quantum ‘heat bath’ really exists? There must be a lot of energy in it; does this have cosmological implications? Could we use it as a power source? The thermally dissipative effects will presumably make the universe ‘run down’ in the end, and one might well ask how long this will take, or whether it should have happened already. Because of the thermodynamic element in the theory, the density matrix plays an important role in the formalism and the quantum treatment is essentially statistical. This makes the familiar quantum ‘measurement problem’ go away, according to the author, but somemay think that it hasmerely been temporarily swept under the carpet. In a furthermajor section, the author develops the theory of quantum electrodynamics in terms of an unconventional approach denoted as BRST quantisation, which replaces gauge symmetry. Unfortunately, the conceptual basis of this is rather complex. His eventual desire is to apply to this area the ideas that he has presented earlier. As always, an important challenge is to provide contact with experiment. It appears that this method may be capable of giving results that are compatible with conventional Lagrangian-based quantum field theory, but with much more effort compensated by greater intellectual satisfaction, in the author’s opinion. As will be clear from the above, this is emphatically not an introductory textbook in quantum field theory, and the greater part of its content is more mathematical than philosophical. The general physicist may find interest in the extended initial philosophical discussion, which prominently features the ideas of Kant and Boltzmann. Öttinger presents a set of ‘metaphysical postulates’, most of which are very general. (In one of them, there is a reference to ‘numerous’ infinities where ‘numerical’ is apparently intended.) They include the idea of thermodynamic quantum dissipation, however, which some would see more as a model assumption. In his theoretical chapters, he tries to mention these principles when he can, and a desire to avoid infinities is certainly justifiable and no doubt philosophical. Still, philosophy of some kind could be said to be implicit in most of physics! The final summary chapter is useful as a statement of what Öttinger believes he has achieved, and of the theoretical work that is still needed. This could be a suitable acquisition for some departmental libraries, but I would suspect that those who wish to purchase it for themselves will mostly be in the ranks of specialists who have already read and been stimulated by the author’s previous publications in these areas.
Monthly Notices of the Royal Astronomical Society, 2021
ABSTRACTObservations in the lowest Murchison Widefield Array (MWA) band between 75 and 100 MHz ha... more ABSTRACTObservations in the lowest Murchison Widefield Array (MWA) band between 75 and 100 MHz have the potential to constrain the distribution of neutral hydrogen in the intergalactic medium at redshift ∼13–17. Using 15 h of MWA data, we analyse systematics in this band such as radio-frequency interference (RFI), ionospheric and wide field effects. By updating the position of point sources, we mitigate the direction-independent calibration error due to ionospheric offsets. Our calibration strategy is optimized for the lowest frequency bands by reducing the number of direction-dependent calibrators and taking into account radio sources within a wider field of view. We remove data polluted by systematics based on the RFI occupancy and ionospheric conditions, finally selecting 5.5 h of the cleanest data. Using these data, we obtain 2σ upper limits on the 21 cm power spectrum in the range of $0.1~ h~{\mathrm{ Mpc}}^{-1}\lessapprox k \lessapprox 1 ~ ~h~{\mathrm{ Mpc}}^{-1}$ and at z = 1...
Monthly Notices of the Royal Astronomical Society, 2020
Cosmic strings are potential gravitational-wave (GW) sources that can be probed by pulsar timing ... more Cosmic strings are potential gravitational-wave (GW) sources that can be probed by pulsar timing arrays (PTAs). In this work we develop a detection algorithm for a GW burst from a cusp on a cosmic string, and apply it to Parkes PTA data. We find four events with a false alarm probability less than 1 per cent. However further investigation shows that all of these are likely to be spurious. As there are no convincing detections we place upper limits on the GW amplitude for different event durations. From these bounds we place limits on the cosmic string tension of Gμ ∼ 10−5, and highlight that this bound is independent from those obtained using other techniques. We discuss the physical implications of our results and the prospect of probing cosmic strings in the era of Square Kilometre Array.
Publications of the Astronomical Society of Australia, 2020
Gravitational waves from coalescing neutron stars encode information about nuclear matter at extr... more Gravitational waves from coalescing neutron stars encode information about nuclear matter at extreme densities, inaccessible by laboratory experiments. The late inspiral is influenced by the presence of tides, which depend on the neutron star equation of state. Neutron star mergers are expected to often produce rapidly rotating remnant neutron stars that emit gravitational waves. These will provide clues to the extremely hot post-merger environment. This signature of nuclear matter in gravitational waves contains most information in the 2–4 kHz frequency band, which is outside of the most sensitive band of current detectors. We present the design concept and science case for a Neutron Star Extreme Matter Observatory (NEMO): a gravitational-wave interferometer optimised to study nuclear physics with merging neutron stars. The concept uses high-circulating laser power, quantum squeezing, and a detector topology specifically designed to achieve the high-frequency sensitivity necessary ...
Volume: The Astronomical Society of the Pacific, ADASS XXV: The 25th Annual ADASS Conference 2017... more Volume: The Astronomical Society of the Pacific, ADASS XXV: The 25th Annual ADASS Conference 2017<br>
Optically levitated nanosensors in high vacuum are excellent candidates for the detection of high... more Optically levitated nanosensors in high vacuum are excellent candidates for the detection of high-frequency gravitational waves, amongst a wider range of other potential applications. We investigate the possibility of detecting high-frequency gravitational waves with levitated opto-mechanics. The current work proposes a laser-cooled optically-levitated nano-sensor to search for a number of highly-energetic sources associated with distant cosmic events, via precision sensing of gravitational waves at micron length scale.
14th Pacific Rim Conference on Lasers and Electro-Optics (CLEO PR 2020), 2020
We propose a small-scale spaceborne probe which uses laser-cooled optically-levitated nanoparticl... more We propose a small-scale spaceborne probe which uses laser-cooled optically-levitated nanoparticles to search for a variety of sources associated with high frequency cosmic events, through high-precision measurements and detection of gravitational waves at micron distances.
We aim to analyze the validity and consistency conditions as well as the generic predictions for ... more We aim to analyze the validity and consistency conditions as well as the generic predictions for string and superstring theory models in low energy physics context, covering a range of challenging ideas that are part of the field, from the Weak Gravity Conjecture, compactifications, string vacua, low-energy supersymmetry, gauge-symmetry breaking and supersymmetry breaking to heterotic strings, D-branes, M-Theory and large dimensions. We identify the theoretical implications, current concerns and experimental constraints of candidate string theories in the low energy limit, that are underlying certain solutions to several nontrivial problems such as the dimensionality of space-time, naturalness, supersymmetry and supergravity, axions and the strong CP problem, Yukawa couplings, black hole information paradox or grand unification. We finally discuss the effective field theory relevant for low energy precision physics at scales probed in table-top laboratory experiments and justify its...
14th Pacific Rim Conference on Lasers and Electro-Optics (CLEO PR 2020), 2020
We propose to extend the search for new physics beyond Standard Model using optically trapped and... more We propose to extend the search for new physics beyond Standard Model using optically trapped and laser cooled dielectric nanoparticles for the resonant detection of short-range forces and corrections to Newtonian gravity.
The aim of this unique monograph is to give a comprehensive review of the development of cosmolog... more The aim of this unique monograph is to give a comprehensive review of the development of cosmological inflation theory, scalar field cosmology, numerical results and simulations. The book provides ...
Classical Field Theory is a graduate level introduction to modern classical field theory, includi... more Classical Field Theory is a graduate level introduction to modern classical field theory, including electromagnetism and general relativity and describes various classical methods for fields with negligible quantum effects. The book is an expanded version of a field theory course in São Paulo. The author focuses on different theoretical solutions that require classical field theory methods, aiming to assist graduate students and researchers in easily make usage of classical field theory methods and adjust to this conceptual level before jumping directly into a course of quantum field theory. The book provides a theoretical framework for understanding fields and the methods associated with them. Most modern methods of classical field theory don’t get included into the standard student curriculum, making this book an invaluable asset. The book makes the transition between classical fields and quantum field theory much smoother and safe. The textbook provides a comprehensive review of classical mechanics, from Lagrangean, equations of motion to the Hamiltonian formalism, conservation laws, canonical transformations and the HamiltonJacobi theory. The author focuses on symmetries, groups, Lie algebras, Abelian Lie group invariance, cyclic groups and representations. The author also reviews the kinematics and dynamics of Special Relativity, Lorentz tensors, covariant Lagrangeans and the Lorentz group. The author defines the notion of field and introduces electromagnetism as a field theory, describing Maxwell’s equations and the EulerLagrange equations. The scalar field, its origins and applications are also present, together with their Lagrangeans, models and the equations of motion. Classical integrability, the continuum limit of discrete, lattice and spin systems are also provided. The book introduces us to the classical perturbation theory, polynomial potential and the formal solutions to the equations of motion. The book also covers the representations of the Lorentz group (Poincaré group, universal cover, Wigner method), rotation matrices, the spin-statistics theorem, Maxwell equation, Abelian vector fields, Proca field, energy-momentum tensor, Maxwell duality, electromagnetic waves and the motion of charged particles. The author describes Hofion solution and Hopf map, complex scalar fields and gauging global symmetries. The book introduces the reader also to the Noether theorem and its applications, nonrelativistic and relativistic fluid dynamics, including fluid vortices and knots. The second part of the book focuses on Solitons and topology as well as Non-Abelian theory (Kink solutions, Sine-Gordon, domain walls and topology, the Skyrmion scalar field, topological numbers, field theory solitons for condensed matter, XY and Rotor model, Spins, superconductivity, Landau-Ginzburg model and the Kosterlitz-Thouless phase transition. The radiation of classical scalar fields (Heisenberg model), Derrick’s theorem, symmetry breaking and the Abelian-Higgs system are also presented, together with the Non-Abelian gauge theory, Yang-Mills equation, Dirac monopole, Diract quantisation, the instanton, nontopological solutions, unstable solitons and moduli space. The last part of the book focuses on other spins or statistics, together with General relativity, from Chern-Simons theory, emergent gauge fields, Quantum Hall effect, Anyon statistics, massive theory, particle-vortex and particle-sting dualities, fermions andDirac spinors or the Dirac equation. The General relativity part contains concepts such as Einstein action and equation, perturbative and non-perturbative gravity, gravitational waves, time-dependent gravity and cosmology, gauges, dimensional reduction, cosmic strings, gravitational instantons and black hole solutions. Each chapter ends with further reading notes and several exercises, allowing the reader to identify the key aspects of the chapter and test their understanding.
Chern–Simons (Super)gravity is based on a suite of lecture notes on gravitational Chern–Simons th... more Chern–Simons (Super)gravity is based on a suite of lecture notes on gravitational Chern–Simons theories developed by two respected experts on general relativity and quantum field theory. Both the b...
one of ‘work in progress’. For this reviewer, some interesting questions can be raised. I wonder ... more one of ‘work in progress’. For this reviewer, some interesting questions can be raised. I wonder how we may ever know if such a quantum ‘heat bath’ really exists? There must be a lot of energy in it; does this have cosmological implications? Could we use it as a power source? The thermally dissipative effects will presumably make the universe ‘run down’ in the end, and one might well ask how long this will take, or whether it should have happened already. Because of the thermodynamic element in the theory, the density matrix plays an important role in the formalism and the quantum treatment is essentially statistical. This makes the familiar quantum ‘measurement problem’ go away, according to the author, but somemay think that it hasmerely been temporarily swept under the carpet. In a furthermajor section, the author develops the theory of quantum electrodynamics in terms of an unconventional approach denoted as BRST quantisation, which replaces gauge symmetry. Unfortunately, the conceptual basis of this is rather complex. His eventual desire is to apply to this area the ideas that he has presented earlier. As always, an important challenge is to provide contact with experiment. It appears that this method may be capable of giving results that are compatible with conventional Lagrangian-based quantum field theory, but with much more effort compensated by greater intellectual satisfaction, in the author’s opinion. As will be clear from the above, this is emphatically not an introductory textbook in quantum field theory, and the greater part of its content is more mathematical than philosophical. The general physicist may find interest in the extended initial philosophical discussion, which prominently features the ideas of Kant and Boltzmann. Öttinger presents a set of ‘metaphysical postulates’, most of which are very general. (In one of them, there is a reference to ‘numerous’ infinities where ‘numerical’ is apparently intended.) They include the idea of thermodynamic quantum dissipation, however, which some would see more as a model assumption. In his theoretical chapters, he tries to mention these principles when he can, and a desire to avoid infinities is certainly justifiable and no doubt philosophical. Still, philosophy of some kind could be said to be implicit in most of physics! The final summary chapter is useful as a statement of what Öttinger believes he has achieved, and of the theoretical work that is still needed. This could be a suitable acquisition for some departmental libraries, but I would suspect that those who wish to purchase it for themselves will mostly be in the ranks of specialists who have already read and been stimulated by the author’s previous publications in these areas.
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