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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

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

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

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

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

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

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 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.

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.

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>
3.

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
4.

Matthew Stephen Fox

Multipole Hair of Schwarzschild-Tangherlini Black Holes

Journal of Mathematical Physics 60 (2019) 102502.
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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.

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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8.

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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9.

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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10.

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.
PDF document
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