Gravity, an unexpected journey: from thermodynamics to emergent gravity, Lorentz breaking and back...
Stefano Liberati SISSA International School for Advanced Studies
11521 - 11532 of 20132 Results
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Probing the electron-proton mass ratio variation with AMO systems
Robin Cote University of Connecticut
PIRSA:14060050Nuclear spin precession of noble gases in ultra low magnetic fields
Lutz Trahms Physikalisch-Technische Bundesanstalt (PTB)
PIRSA:14060033Optical magnetometry - From basics to Global Network of Optical Magnetometer for Exotic physics
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Nathan Leefer University of California, Berkeley
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Szymon Pustelny University of California, Berkeley
PIRSA:14060032-
Free Discussion
PIRSA:14060031Search for new physics in atoms: cosmic PNC and variation of alpha
Vladimir Dzuba University of New South Wales (UNSW)
PIRSA:14060030Axion-induced effects and topological defect dark matter detection schemes
Yevgeny Stadnik University of New South Wales (UNSW)
PIRSA:14060028Analogue Models of Gravity: The ubiquitous space-time
Stefano Liberati SISSA International School for Advanced Studies
Astrophysical and cosmological aspects of feebly-interacting light species
Josef Pradler Austrian Academy of Sciences
PIRSA:14060027
Gravity, an unexpected journey: from thermodynamics to emergent gravity, Lorentz breaking and back...
Stefano Liberati SISSA International School for Advanced Studies
Thermodynamical aspects of gravity have been a tantalising puzzle for more than forty years now and are still at the center of much activity in semiclassical and quantum gravity. We shall explore the possibility that they might hint toward an emergent nature of gravity exploring the possible implications of such hypothesis. Among these we shall focus on the possibility that Lorentz invariance might be only a low energy/emergent feature by discussing viable theoretical frameworks, present constraints and open issues which make this path problematic. In the end we shall focus on black hole thermodynamics in Lorentz breaking gravity by presenting some recent results that seems to hint towards a surprising resilience of thermodynamics aspect of gravity even in these scenarios.Probing the electron-proton mass ratio variation with AMO systems
Robin Cote University of Connecticut
PIRSA:14060050Atomic magnetometers for precision measurements
Mike Romalis Princeton University
PIRSA:14060034Atomic magnetometers have a long history in tests of Standard Model since they provide sensitive constraints on new spin interactions. I will review recent progress in magnetometry using electron and nuclear spins, describe some of the limits set on new physics and discuss ideas for future experiments.Nuclear spin precession of noble gases in ultra low magnetic fields
Lutz Trahms Physikalisch-Technische Bundesanstalt (PTB)
PIRSA:14060033In the low energy re¬gime, precision measurements of spin precession have gained increased attention as an alternative pathway to physics beyond the standard model. These measurements aim at the detection of minute frequency changes superimposed on low Larmor frequencies at extremely weak magnetic fields. Such measurements require an effective shielding against the magnetic field of the Earth and other perturbations. For measuring the precession frequency with high precision, a long lifetime of the precessing nuclear magnetization is required, thus the homogeneity of the applied field is a crucial parameter. In addition, criteria are needed that unambiguously distinguish magnetic artifacts from the non-magnetic exotic interactions that we search for. This can be accomplished by the concept of co-magnetometry, i.e., by simultaneous measuring the precession of two nuclear species such as 3He and 129Xe. Yet another kind of co-magnetometry is the use of SQUIDs for monitoring the spin precession. SQUIDs are magnetic field detectors of their own kind, which can measure the oscillating magnetic field generated by the precessing nuclear magnetic moment as well as the magnetic dc background field. In this presentation, I will report on the current state of the art in our lab in measurements of nuclear spin precession of noble gases.Optical magnetometry - From basics to Global Network of Optical Magnetometer for Exotic physics
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Nathan Leefer University of California, Berkeley
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Szymon Pustelny University of California, Berkeley
PIRSA:14060032In our talk we seek to present a broad overview of the field of optical magnetometers, starting from basic principles to fundamental limitations to the variety of applications in which they have already found use. We will end with a report on the development of a new worldwide network of synchronized magnetometers that can be used to search for a variety of new physical phenomena (many of which are discussed at this conference!).-
Free Discussion
PIRSA:14060031Search for new physics in atoms: cosmic PNC and variation of alpha
Vladimir Dzuba University of New South Wales (UNSW)
PIRSA:14060030We consider pseudo-scalar and pseudo-vector interaction of atomic electrons with hypothetical dark matter particles (e.g., axions). These interactions lead to oscillating atomic parity non-conserving (PNC) amplitudes and/or oscillating electric dipole moments (EDM). In static
limit for PNC, existing atomic PNC experiments can be used to constrain time component of the pseudo-vector field.
Possible variation of fundamental constants is suggested by theories unifying gravity with other interactions. Evidence of the space/time variation of the fine structure constant alpha is found in
the quasar absorption spectra. Optical transitions in highly charged ions can be used as sensitive tools for studying time variation of alpha in laboratory.Axion-induced effects and topological defect dark matter detection schemes
Yevgeny Stadnik University of New South Wales (UNSW)
PIRSA:14060028We discuss new observable effects of axionic dark matter in atoms, molecules and nuclei. We show that the interaction of an axion field, or in general a pseudoscalar field, with the axial-vector current generated by an electron through a derivative-type coupling can give rise to a time-dependent mixing of opposite-parity states in atomic and molecular systems. Likewise, the analogous interaction of an axion field with the axial-vector current generated by a nucleon can give rise to time-dependent mixing of opposite-parity states in nuclear systems. This mixing can induce oscillating electric dipole moments, oscillating parity nonconservation effects and oscillating anapole moments in such systems. By adjusting the energy separation between the opposite-parity states of interest to match the axion mass energy, axion-induced experimental observables can be enhanced by many orders of magnitude. Oscillating atomic electric dipole moments can also be generated by axions through hadronic mechanisms, namely the P,T-violating nucleon-nucleon interaction and through the axion-induced electric dipole moments of valence nucleons, which comprise the nuclei. The axion field is modified by Earth’s gravitational field. The interaction of the spin of either an electron or nucleon with this modified axion field leads to axion-induced observable effects. These effects, which are of the form g • σ, differ from the axion-wind effect, which has the form pa • σ.
We also propose schemes for the detection of topological defect dark matter using pulsars and other luminous extraterrestrial systems via non-gravitational signatures. The dark matter field, which makes up a defect, may interact with standard model particles, including quarks and the photon, resulting in the alteration of their masses. When a topological defect passes through a pulsar, its mass, radius and internal structure may be altered, resulting in a pulsar `quake'. A topological defect may also function as a cosmic dielectric material with a frequency-dependent index of refraction, which would give rise to the time delay of a periodic extraterrestrial light or radio signal, and the dispersion of a light or radio source in a similar manner to an optical lens. The biggest advantage of such astrophysical observations over recently proposed terrestrial detection methods is the much higher probability of a defect been found in the vast volumes of outer space compared with one passing through Earth itself.
References: (1) Phys. Rev. D 89, 043522 (2014).
(2) arXiv:1404.2723.
(3) arXiv:1405.5337.Analogue Models of Gravity: The ubiquitous space-time
Stefano Liberati SISSA International School for Advanced Studies
Analogies have played a very important role in physics and mathematics, as they provide new ways of looking at problems that permit cross-fertilization of ideas among different branches of science. An analogue gravity model is a generic dynamical system (typically but not always based on condensed matter physics) where the propagation of excitations/perturbations can be described via hyperbolic equations of motion possibly characterized be one single metric element for all the perturbations. We shall review the historical development of this field, some of the systems proposed, and discuss several applications of this fruitful analogy mainly in the context of black hole physics and cosmology. While typical applications are in the realm of classical and quantum field theory on curved spacetime, I shall in the end also discuss recent developments which may provide insights about the possible nature of gravitational dynamics in emergent gravity scenarios.Astrophysical and cosmological aspects of feebly-interacting light species
Josef Pradler Austrian Academy of Sciences
PIRSA:14060027More often than not, astrophysical probes are superior to direct laboratory tests when considering light, very weekly interacting particles and it takes clever strategies and/or ultra-pure experimental setups for direct tests to be competitive. In this talk, I will review the astrophysical side of the story with a particular focus on dark photons and axion-like particles. I will also present some recent results on the emission process of dark photons with mass below 10 keV from the interior of stars. Compared to previous analyses, limits on dark photons are significantly improved, to the extent that many dedicated experimental searches find themselves inside astrophysically excluded regions. However, constraints on the atomic ionization rate from a solar flux imposed by Dark Matter experiments offer a new test of such states, surpassing even the most stringent astrophysical limits. The model also serves as a prototype scenario for energy injection in the early Universe and I will show how cosmology offers unique sensitivity when laboratory probes are out of reach. Time permitting, I may also briefly comment on very light axions and their cosmology.Cosmological Constraints on Ultra-light Axions
David Marsh King's College London
PIRSA:14060026Ultra-light axions (ULAs) with masses in the range 1e-33 eV< m < 1e-18 eV can constitute a novel component of the dark matter, which can be constrained by cosmological observations. ULA dark matter (DM) is produced non-thermally via vacuum realignment in the early universe and is cold. Pressure perturbations, however, manifest a scale in the clustering (also the de Broglie scale). For the range of masses considered this spans the Hubble scale down to sub-galactic scales. In the model-independent adiabatic mode of initial conditions, one can gain strong constraints on ULAs as DM from the CMB and large scale structure (LSS). I will present constraints from Planck and WiggleZ, constraining m~1e-33 eV to 1e-25 eV at the percent level. In the range m\gtrsim 1e-22 eV ULAs may also solve the "small-scale problems" of CDM, and suggest other constraints from LSS and high-z observations, constraining m\lesssim 1e-22 eV to be sub-dominant in DM. Future prospects from CMB lensing, and from Euclid galaxy weak lensing, will make sub-percent constraints out to m~1e-21 eV. Model-dependent couplings between axions and photons provide still other bounds from CMB spectral distortions. Finally, if the inflationary energy scale is high, corresponding to an observable tensor-to-scalar ratio, then CMB isocurvature perturbations provide the strongest constraints on m>1e-24 eV, ruling out ULA dark matter in the simplest inflationary scenarios over the entire range considered, as well as the "anthropic window" for the QCD axion.