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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

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

The size dependence of the dielectric constants of barium titanate or other ferroelectric particles can be explored by embedding particles into an epoxy matrix whose dielectric constant can be measured directly. However, to extract the particle dielectric constant requires a model of the composite medium. We compare a finite-element model for various volume fractions and particle arrangements to several effective-medium approximations, which do not consider particle arrangement explicitly. For a fixed number of particles, the composite dielectric constant increases with the degree of agglomeration, and we relate this increase to the number of regions of enhanced electric field along the applied field between particles in an agglomerate. Additionally, even for dispersed particles, we find that the composite method of assessing the particle dielectric constant may not be effective if the particle dielectric constant is too high compared to the background medium dielectric constant.

Abstract

Mechanical power limitations emerge from the physical trade-off between force and velocity. Many biological systems incorporate power-enhancing mechanisms enabling extraordinary accelerations at small sizes. We establish how power enhancement emerges through the dynamic coupling of motors, springs, and latches and reveal how each displays its own force-velocity behavior. We mathematically demonstrate a tunable performance space for spring-actuated movement that is applicable to biological and synthetic systems. Incorporating nonideal spring behavior and parameterizing latch dynamics allows the identification of critical transitions in mass and trade-offs in spring scaling, both of which offer explanations for long-observed scaling patterns in biological systems. This analysis defines the cascading challenges of power enhancement, explores their emergent effects in biological and engineered systems, and charts a pathway for higher-level analysis and synthesis of power-amplified systems.

Abstract

We demonstrate that rare decays of the Standard Model \( Z \) boson can be used to discover and characterize the nature of new hidden-sector particles. We propose new searches for these particles in soft, high-multiplicity leptonic final states at the Large Hadron Collider. The proposed searches are sensitive to low-mass particles produced in \( Z \) decays, and we argue that these striking signatures can shed light on the hidden-sector couplings and mechanism for mass generation.

Abstract

Photons from distant astronomical sources can be used as a classical source of randomness to improve fundamental tests of quantum nonlocality, wave-particle duality, and local realism through Bell’s inequality and delayed-choice quantum eraser tests inspired by Wheeler’s cosmic-scale Mach-Zehnder interferometer gedanken experiment. Such sources of random numbers may also be useful for information-theoretic applications such as key distribution for quantum cryptography. Building on the design of an astronomical random number generator developed for the recent cosmic Bell experiment [Handsteiner et al. Phys. Rev. Lett. 118, 060401 (2017)], in this paper we report on the design and characterization of a device that, with 20-nanosecond latency, outputs a bit based on whether the wavelength of an incoming photon is greater than or less than ≈700 nm. Using the one-meter telescope at the Jet Propulsion Laboratory Table Mountain Observatory, we generated random bits from astronomical photons in both color channels from 50 stars of varying color and magnitude, and from 12 quasars with redshifts up to \( z = 3.9 \). With stars, we achieved bit rates of \( \sim1 \times 10^6\,\mathrm{Hz/m^2} \), limited by saturation of our single-photon detectors, and with quasars of magnitudes between 12.9 and 16, we achieved rates between \( \sim 10^2 \) and \( 2 \times 10^3 \,\mathrm{Hz/m^2} \). For bright quasars, the resulting bitstreams exhibit sufficiently low amounts of statistical predictability as quantified by the mutual information. In addition, a sufficiently high fraction of bits generated are of true astronomical origin in order to address both the locality and freedom-of-choice loopholes when used to set the measurement settings in a test of the Bell-CHSH inequality.

Abstract

We find that laser-induced local melting attracts and deforms grain boundaries in 2D colloidal crystals. When a melted region in contact with the edge of a crystal grain recrystallizes, it deforms the grain boundarythis attraction is driven by the multiplicity of deformed grain boundary configurations. Furthermore, the attraction provides a method to fabricate artificial colloidal crystal grains of arbitrary shape, enabling new experimental studies of grain boundary dynamics and ultimately hinting at a novel approach for fabricating materials with designer microstructures.

Abstract

Hydrodynamic slip, the motion of a liquid along a solid surface, represents a fundamental phenomenon in fluid dynamics that governs liquid transport at small scales. For polymeric liquids, de Gennes predicted that the Navier boundary condition together with polymer reptation implies extraordinarily large interfacial slip for entangled polymer melts on ideal surfaces; this Navier-de Gennes model was confirmed using dewetting experiments on ultra-smooth, low-energy substrates. Here, we use capillary leveling-surface tension driven flow of films with initially non-uniform thickness-of polymeric films on these same substrates. Measurement of the slip length from a robust one parameter fit to a lubrication model is achieved. We show that at the low shear rates involved in leveling experiments as compared to dewetting ones, the employed substrates can no longer be considered ideal. The data is instead consistent with a model that includes physical adsorption of polymer chains at the solid/liquid interface.

Abstract

The physical properties of glassy polymer films change as they become confined. These changes are often attributed to increased average molecular mobility and reduction in entanglement density. Both are known to alter mechanical behavior, including the formation of strain localizations, e.g., crazing and shear deformation zones. Here, we determine how the entanglement density and surface mobility change the mechanical behavior of a glassy polymer film when it becomes confined. We utilize a custom-built uniaxial tensile tester for ultrathin films and dark-field optical microscopy to characterize the complete stress strain response and the associated strain localizations for ultrathin polystyrene films of varying thickness (h(F) = 20-360 nm). These experiments provide direct measurement of the stress in a craze as well as the stresses involved through the transition from crazing to shear deformation zones. Most significantly, we observe a transition in strain localization from crazing to shear deformation zones as film thickness changes from 30 to 20 nm, providing new insights into how the surfaces alter the mechanical behavior in confined polymer films.

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

1.

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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2.

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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Breznay2019a
3.

Jonas Leif Kaufman, Scott H. Tan, Kirklann Lau, Ashka Shailesh Shah, Robert G. Gambee, Christopher P. Gage, Lupe Maria MacIntosh, Albert Dato, Peter N. Saeta, Richard C. Haskell, and Todd C. Monson

Permittivity effects of particle agglomeration in ferroelectric ceramic-epoxy composites using finite element modeling

AIP Advances 8 (2018) 125020.
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4.

Mark Ilton, M. Saad Bhamla, Xiaotian Ma, Suzanne M. Cox, Leah L. Fitchett, Yongjin Kim, Je-sung Koh, Deepak Krishnamurthy, Chi-Yun Kuo, Fatma Zeynep Temel, Alfred J. Crosby, Manu Prakash, Gregory P. Sutton, Robert J. Wood, Emanuel Azizi, Sarah Bergbreiter, and S. N. Patek

The principles of cascading power limits in small, fast biological and engineered systems

Science 360 (2018) 397+.
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5.

Nikita Blinov, Eder Izaguirre, and Brian Shuve

Rare Z Boson Decays to a Hidden Sector

Physical Review D 97 (2018) 015009.
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Shuve PRD 97, 015009
6.

Calvin Leung, Amy Frances Brown, Hien Nguyen, Andrew S. Friedman, David I. Kaiser, and Jason Gallicchio

Astronomical Random Numbers for Quantum Foundations Experiments

Physical Review A 97 (2018) 042120.
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7.

Caitlin Ellen Cash, Jeremy Wang, Maya Maria Martirossyan, Kemper Ludlow, Alejandro E. Baptista, Nina M. Brown, Eli Joseph Weissler, Jatin Abacousnac, and Sharon Gerbode

Local Melting Attracts Grain Boundaries in Colloidal Polycrystals

Physical Review Letters 120 (2018) 018002.
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8.

Mark Ilton, Thomas Salez, Paul D. Fowler, Marco Rivetti, Mohammed Aly, Michael Benzaquen, Joshua D. McGraw, Elie Raphael, Kari Dalnoki-Veress, and Oliver Baeumchen

Adsorption-induced slip inhibition for polymer melts on ideal substrates

Nature Communications 9 (2018) .
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9.

R. Konane Bay, Shinichiro Shimomura, Yujie Liu, Mark Ilton, and Alfred J. Crosby

Confinement Effect on Strain Localizations in Glassy Polymer Films

Macromolecules 51 (2018) 3647-3653.
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10.

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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