Abstract

The inherent force–velocity trade-off of muscles and motors can be overcome by instead loading and releasing energy in springs to power extreme movements. A key component of this paradigm is the latch that mediates the release of spring energy to power the motion. Latches have traditionally been considered as switches; they maintain spring compression in one state and allow the spring to release energy without constraint in the other. Using a mathematical model of a simplified contact latch, we reproduce this instantaneous release behaviour and also demonstrate that changing latch parameters (latch release velocity and radius) can reduce and delay the energy released by the spring. We identify a critical threshold between instantaneous and delayed release that depends on the latch, spring, and mass of the system. Systems with stiff springs and small mass can attain a wide range of output performance, including instantaneous behaviour, by changing latch release velocity. We validate this model in both a physical experiment as well as with data from the Dracula ant, Mystrium camillae, and propose that latch release velocity can be used in both engineering and biological systems to control energy output.

Abstract

We propose a simple model in which the baryon asymmetry and dark matter are created via the decays and inverse decays of QCD-triplet scalars, at least one of which must be in the TeV mass range. Singlet fermions produced in these decays constitute the dark matter. The singlets never reach equilibrium, and their coherent production, propagation, and annihilation generates a baryon asymmetry. We find that the out-of-equilibrium condition and the dark matter density constraint typically require the lightest scalar to be long-lived, giving good prospects for detection or exclusion in current and upcoming colliders. In generalizing the leptogenesis mechanism of Akhmedov, Rubakov and Smirnov, our model expands the phenomenological possibilities for low-scale baryogenesis.

Abstract

Charge order is now accepted as an integral constituent of cuprate high-temperature superconductors, one that is intimately related to other electronic instabilities including anti-ferromagnetism and superconductivity. Unlike conventional Peierls density waves, the charge correlations in cuprates have been predicted to display a rich momentum space topology depending on the underlying fermiology. However, charge order has only been observed along the high-symmetry Cu–O bond directions. Here, using resonant soft X-ray scattering, we investigate the evolution of the full momentum space topology of charge correlations in \( T'-\mathrm{(Nd,Pr)_2 CuO_4} \) as a function of electron doping. We report that, when the parent Mott insulator is doped, charge correlations first emerge with full rotational symmetry in momentum space, indicating glassy charge density modulation in real space possibly seeded by local defects. At higher doping levels, the orientation of charge correlations is locked to the Cu–O bond directions, restoring a more conventional long-ranged bidirectional charge order. Through charge susceptibility calculations, we reproduce the evolution in topology of charge correlations across the antiferromagnetic phase boundary and propose a revised phase diagram of \( T'-\mathrm{Ln_2 CuO_4} \) with a superconducting region extending toward the Mott limit.

Abstract

We study the field of an electric point charge that is slowly lowered into an \( n + 1 \) dimensional Schwarzschild-Tangherlini black hole. We find that if \( n > 3 \), then countably infinite nonzero multipole moments manifest to observers outside the event horizon as the charge falls in. This suggests the final state of the black hole is not characterized by a Reissner-Nordström-Tangherlini geometry. Instead, for odd \( n \), the final state either possesses a degenerate horizon, undergoes a discontinuous topological transformation during the infall of the charge, or both. For even \( n \), the final state is not guaranteed to be asymptotically flat.

Abstract

The discovery of quantum oscillations in hole- and electron-doped cuprate families has underscored the importance of the Fermi surface in cuprate superconductivity. While the observed quantum oscillations in both families have revealed the presence of reconstructed Fermi surfaces, there remains an important distinction between the two. In hole-doped cuprates the oscillations are thought to arise from the effects of a charge density wave, while in the electron-doped cuprates it is thought that these oscillations occur from an antiferromagnetically reconstructed Fermi surface, despite the fact that the oscillations are observed in overdoped compounds, far from the putative antiferromagnetic critical point. In this work we study thin films of \( \mathrm{Pr_Cu O_{4 \pm \delta}} \), whose apparent doping can be finely tuned by annealing, allowing studies of quantum oscillations in samples straddling the critical point. We show that even though there is a mass enhancement of the quasiparticles, there are only small changes to the Fermi surface itself, suggesting that charge order is a more likely origin, with electronic correlations that are strongly dependent on the structural parameters.

Abstract

We investigate Palatini \( f( \mathcal{R}, \mathcal{L}_m, \mathcal{R}_{\mu\nu}T^{\mu\nu}) \) modified theories of gravity. As such, the metric and affine connection are treated as independent dynamical fields, and the gravitational Lagrangian is made a function of the Ricci scalar \( \mathcal{R} \), the matter Lagrangian density \( \mathcal{L}_{m} \), and a “matter-curvature scalar” \( \mathcal{R}_{\mu\nu}T^{\mu\nu} \). The field equations and the equations of motion for massive test particles are derived, and we find that the independent connection can be expressed as the Levi-Civita connection of an auxiliary, energy momentum–dependent metric that is related to the physical metric by a matrix transformation. Similar to metric \( f(\mathcal{R}, T, \mathcal{R}_{\mu\nu}T^{\mu\nu}) \) gravity, the field equations impose the nonconservation of the energy- momentum tensor, leading to the appearance of an extra force on massive test particles. We obtain the explicit form of the field equations for massive test particles in the case of a perfect fluid and an expression for the extra force. The nontrivial modifications to scalar fields and both linear and nonlinear electrodynamics are also considered. Finally, we detail the conditions under which the present theory is equivalent to the Eddington-inspired Born-Infeld theory of gravity.

Abstract

The description of disorder-induced electron localization by Anderson over 60 years ago began a quest for novel phenomena emerging from electronic interactions in the presence of disorder. Even today, the interplay of interactions and disorder remains incompletely understood. This holds in particular for strongly disordered materials where charge transport depends on ‘hopping’ between localized sites. Here we report an unexpected spin sensitivity of the electrical conductivity at the transition from diffusive to hopping conduction in a material that combines strong spin-orbit coupling and weak inter-electronic interactions. In thin films of the disordered crystalline phase change material \( \mathrm{SnSb_2 Te_4} \), a distinct change in electrical conductance with applied magnetic field is observed at low temperatures. This magnetoconductance changes sign and becomes anisotropic at the disorder-driven crossover from strongly localized (hopping) to weakly localized (diffusive) electron motion. The positive and isotropic magnetoconductance arises from disruption of spin correlations that inhibit hopping transport. This experimental observation of a recently hypothesized “spin memory” demonstrates the spin plays a previously overlooked role in the disorder-driven transition between weak and strong localization in materials with strong spin–orbit interactions.

Abstract

We study the potential of the LHCb experiment to discover, for the first time, the true muonium bound state. We propose a search for the vector state, which kinetically mixes with the photon and dominantly decays to electron-positron pairs. We demonstrate that a search for true muonium produced in eta meson decays and decaying at a displaced vertex can exceed a significance of 5 standard deviations assuming statistical uncertainties. We present two possible searches: an inclusive search for the electron-positron vertex, and an exclusive search which requires an additional photon and a reconstruction of the eta mass.

Abstract

We examine the theoretical motivations for long-lived particle (LLP) signals at the LHC in a comprehensive survey of standard model (SM) extensions. LLPs are a common prediction of a wide range of theories that address unsolved fundamental mysteries such as naturalness, dark matter, baryogenesis and neutrino masses, and represent a natural and generic possibility for physics beyond the SM (BSM). In most cases the LLP lifetime can be treated as a free parameter from the µm scale up to the Big Bang Nucleosynthesis limit of \( \sim 10^7\;\mathrm{m} \). Neutral LLPs with lifetimes above ~100 m are particularly difficult to probe, as the sensitivity of the LHC main detectors is limited by challenging backgrounds, triggers, and small acceptances. MATHUSLA is a proposal for a minimally instrumented, large-volume surface detector near ATLAS or CMS. It would search for neutral LLPs produced in HL-LHC collisions by reconstructing displaced vertices (DVs) in a low-background environment, extending the sensitivity of the main detectors by orders of magnitude in the long-lifetime regime. We study the LLP physics opportunities afforded by a MATHUSLA-like detector at the HL-LHC, assuming backgrounds can be rejected as expected. We develop a model-independent approach to describe the sensitivity of MATHUSLA to BSM LLP signals, and compare it to DV and missing energy searches at ATLAS or CMS. We then explore the BSM motivations for LLPs in considerable detail, presenting a large number of new sensitivity studies. While our discussion is especially oriented towards the long-lifetime regime at MATHUSLA, this survey underllnes the importance of a varied LLP search program at the LHC in general. By synthesizing these results into a general discussion of the top-down and bottom-up motivations for LLP searches, it is our aim to demonstrate the exceptional strength and breadth of the physics case for the construction of the MATHUSLA detector.

Abstract

Uninhabited aerial vehicle synthetic aperture radar (UAVSAR) observations 2009–2017 of the Yuha Desert area and Global Positioning System (GPS) time series encompassing the region reveal a northward migrating pattern of deformation following the 4 April 2010 \( M_w \) 7.2 El Mayor‐Cucapah (EMC) earthquake. The north end of the EMC rupture exhibits an asymmetric pattern of deformation that is substantial and smooth northeast of the rupture and limited but with surface fracturing slip northwest. The earthquake triggered ~1 cm of surface coseismic slip at the Yuha fault, which continued to slip postseismically. 2.5 cm of Yuha fault slip occurred by the time of the 15 June 2010 \( M_w \) 5.7 Ocotillo aftershock and 5 cm of slip occurred by 2017 following a logarithmic afterslip decay 16‐day timescale. The Ocotillo aftershock triggered 1.4 cm of slip on a northwest trend extending to the Elsinore fault and by 7 years after the EMC earthquake 2.4 cm of slip had accumulated with a distribution following an afterslip function with a 16‐day timescale consistent with other earthquakes and a rate strengthening upper crustal sedimentary layer. GPS data show broad coseismic uplift of the Salton Trough and delayed postseismic motion that may be indicative of fluid migration there and subsidence west of the rupture extension, which continues following the earthquake. The data indicate that the Elsinore, Laguna Salada, and EMC ruptures are part of the same fault system. The results also suggest that north‐south shortening and east‐west extension across the region drove fracture advancing step tectonics north of the EMC earthquake rupture.

Recent Publications

Student authorFaculty author    

11.

Sathvik Divi, Xiaotian Ma, Mark Ilton, Ryan St. Pierre, Babak Eslami, S. N. Patek, and Sarah Bergbreiter

Latch-Based Control of Energy Output in Spring Actuated Systems

Journal of the Royal Society Interface 17 (2020) 20200070.
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12.

Brian Shuve and David Tucker-Smith

Baryogenesis and Dark Matter From Freeze-In

Physical Review D 101 (2020) 115023.
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13.

Mingu Kang, Jonathan Pelliciari, Alex Frano, Nicholas P. Breznay, Enrico Schierle, Eugen Weschke, Ronny Sutarto, Yuwei He, Padraic Shafer, Elke Arenholz, Mo Chen, Keto Zhang, Alejandro Ruiz, Zeyu Hao, Sylvia Lewin, James Analytis, Yoshiharu Krockenberger, Hideki Yamamoto, Kausik Das, and Riccardo Comin

Evolution of Charge Order Topology Across a Magnetic Phase Transition in Cuprate Superconductors

Nature Physics 15 (2019) 335–340.
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14.

Matthew Stephen Fox

Multipole Hair of Schwarzschild-Tangherlini Black Holes

Journal of Mathematical Physics 60 (2019) 102502.
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15.

Nicholas P. Breznay, Corey Hayes, Nityan L Nair, Toni Helm, James G Analytis, Ross D McDonald, Zengwei Zhu, Yoshiharu Krockenberger, Hiroshi Irie, Hideki Yamamoto, K A Modic, Alex Frano, Padraic Shafer, and Elke Arenholz

Interplay of Structure and Charge Order Revealed by Quantum Oscillations in Thin Films of \( \mathrm{Pr_2 Cu O_{4 \pm\delta}} \)

Physical Review B 100 (2019) 235111.
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16.

Matthew Stephen Fox

Palatini \( f(\mathcal{R}, \mathcal{L}_m, \mathcal{R}_{\mu\nu} T^{\mu\nu}) \) gravity and its Born-Infeld semblance

Physical Review D 99 (2019) 124027.
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17.

Johannes Reindl, Hanno Volker, Nicholas P. Breznay, and Matthias Wuttig

Persistence of Spin Memory in a Crystalline, Insulating Phase-Change Material

Npj Quantum Materials 4 (2019) 1–7.
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18.

Xabier Cid Vidal, Philip Ilten, Jonathan Plews, Brian Shuve, and Yotam Soreq

Discovering True Muonium At LHCb

Physical Review D 100 (2019) 053003.
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<p>Dark photon parameter space in dark photon mass and kinetic mixing with (gray) previous limits and future reach from (magenta) Belle II, (purple) FASER, (cyan) HPS, and (green/yellow) LHCb. TM corresponds to the marked point, using Eqs. (2) and (3).</p>
19.

David Curtin, Marco Drewes, John C. McCullough, Patrick Meade, Rabindra N Mohapatra, Jessie Shelton, Brian Shuve, Elena Accomando, Cristiano Alpigiani, Stefan Antusch, Juan Carlos Arteaga-Velázquez, Brian Batell, Martin Bauer, Nikita Blinov, Karen Salomé Caballero-Mora, Jae Hyeok Chang, Eung Jin Chun, Raymond T Co, Timothy Cohen, Peter Cox, Nathaniel Craig, Csaba Csáki, Yanou Cui, Francesco D'Eramo, Luigi Delle Rose, P S Bhupal Dev, Keith R Dienes, Jeff A Dror, Rouven Essig, Jared A Evans, Jason L Evans, Arturo Fernández Tellez, Oliver Fischer, Thomas Flacke, Anthony Fradette, Claudia Frugiuele, Elina Fuchs, Tony Gherghetta, Gian F Giudice, Dmitry Gorbunov, Rick S Gupta, Claudia Hagedorn, Lawrence J Hall, Philip Harris, Juan Carlos Helo, Martin Hirsch, Yonit Hochberg, Anson Hook, Alejandro Ibarra, Seyda Ipek, Sunghoon Jung, Simon Knapen, Eric Kuflik, Zhen Liu, Salvator Lombardo, H J Lubatti, David McKeen, Emiliano Molinaro, Stefano Moretti, Natsumi Nagata, Matthias Neubert, Jose Miguel No, Emmanuel Olaiya, Gilad Perez, Michael E Peskin, David Pinner, Maxim Pospelov, Matthew Reece, Dean J Robinson, Mario Rodríguez Cahuantzi, Rinaldo Santonico, Matthias Schlaffer, Clair Shepherd-Themistocleous, Andrew Spray, Daniel Stolarski, Martin A Subieta Vasquez, Raman Sundrum, Andrea Thamm, Brooks Thomas, Yuhsin Tsai, Brock Tweedie, Stephen M West, Charles Young, Felix Yu, Bryan Zaldivar, Yongchao Zhang, Kathryn Zurek, and José Zurita

Long-Lived Particles At the Energy Frontier: the Mathusla Physics Case

Reports on Progress in Physics 82 (2019) 116201.
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20.

Andrea Donnellan, Jay Parker, Michael Heflin, Gregory A. Lyzenga, Angelyn W. Moore, Lisa Grant Ludwig, John Rundle, Jun Wang, and Marlon Pierce

Fracture Advancing Step Tectonics Observed in the Yuha Desert and Ocotillo, CA, Following the 2010 Mw 7.2 El Mayor-Cucapah Earthquake

Earth and Space Science (2018) .
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