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Physics

Smith College

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Full-Text Articles in Physical Sciences and Mathematics

Wide Range Thin-Film Ceramic Metal-Alloy Thermometers With Low Magnetoresistance, Nathanael Fortune, Joyce E. Palmer-Fortune, A. Trainer, A. Bangura, N. Kondedan, A. Rydh Nov 2023

Wide Range Thin-Film Ceramic Metal-Alloy Thermometers With Low Magnetoresistance, Nathanael Fortune, Joyce E. Palmer-Fortune, A. Trainer, A. Bangura, N. Kondedan, A. Rydh

Physics: Faculty Publications

Many thermal measurements in high magnetic fields require thermometers that are sensitive over a wide temperature range, are low mass, have a rapid thermal response, and have a minimal, easily correctable magnetoresistance. Here we report the development of a new granular-metal oxide ceramic composite (cermet) for this purpose formed by co-sputtering of the metallic alloy nichrome Ni0.8Cr0.2 and the insulator silcon dioxide SiO2. The resulting thin films are sensitive enough to be used from room temperature down to below 100 mK in magnetic fields up to at least 35 tesla.

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Magnetoquantum Oscillations In The Specific Heat Of A Topological Kondo Insulator, Patrick G. Labarre, Andreas Rydh, J. Palmer-Fortune, J. A. Frothingham, S. T. Hannahs, Arthur P. Ramirez, Nathanael Alexander Fortune Sep 2022

Magnetoquantum Oscillations In The Specific Heat Of A Topological Kondo Insulator, Patrick G. Labarre, Andreas Rydh, J. Palmer-Fortune, J. A. Frothingham, S. T. Hannahs, Arthur P. Ramirez, Nathanael Alexander Fortune

Physics: Faculty Publications

Surprisingly, magnetoquantum oscillations (MQO) characteristic of a metal with a Fermi surface have been observed in measurements of the topological Kondo insulator SmB6. As these MQO have only been observed in measurements of magnetic torque (dHvA) and not in measurements of magnetoresistance (SdH), a debate has arisen as to whether the MQO are an extrinsic effect arising from rareearth impurities, defects, and/or aluminum inclusions or an intrinsic effect revealing the existence of charge-neutral excitations. We report here the first observation of magnetoquantum oscillations in the low-temperature specific heat of SmB6. The observed frequencies and their angular dependence for these flux-grown …

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Quantum Counter-Terms For Lattice Field Theory On Curved Manifolds, Evan K. Owen, Casey E. Berger, Richard C. Brower, George T. Fleming, Andrew D. Gasbarro, Timothy G. Raben Jul 2022

Quantum Counter-Terms For Lattice Field Theory On Curved Manifolds, Evan K. Owen, Casey E. Berger, Richard C. Brower, George T. Fleming, Andrew D. Gasbarro, Timothy G. Raben

Physics: Faculty Publications

We present the necessity of counter-terms for Quantum Finite Element (QFE) simulations of ϕ4 theory on non-trivial simplicial manifolds with semi-regular lattice spacing. By computing the local cut-off dependence of UV divergent diagrams we found that the symmetries of the continuum theory are restored for ϕ4 theory on the manifolds S2 and S2 × R in the weak coupling regime [1, 2]. Here we consider the construction of non-perturbative local counter-terms in an attempt to approach the strong coupling Wilson-Fisher IR fixed point.

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Prospects For Lattice Qfts On Curved Riemann Manifolds, Richard C. Brower, Casey E. Berger, George T. Fleming, Andrew D. Gasbarro, Evan K. Owen, Timothy G. Raben, Chung I. Tan, Evan S. Weinberg Jul 2022

Prospects For Lattice Qfts On Curved Riemann Manifolds, Richard C. Brower, Casey E. Berger, George T. Fleming, Andrew D. Gasbarro, Evan K. Owen, Timothy G. Raben, Chung I. Tan, Evan S. Weinberg

Physics: Faculty Publications

Conformal or near conformal Quantum Field Theories QFT) would benefit from a rigorous non-perturbative lattice formulation beyond the flat Euclidean space, Rd. Although all UV complete QFT are generally acknowledged to be perturbatively renormalizable on smooth Riemann manifolds, non-perturbative realization on simplicial lattices (triangulation) encounter difficulties as the UV cut-off is removed. We review the Quantum Finite Element (QFE) method that combines classical Finite Element with new quantum counter terms designed to address this. The construction for maximally symmetric spaces (Sd, R × Sd−1 and AdSd+1) is outlined with numerical tests on R × S2 and a description of theoretical …

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Absolute Frequency Measurement Of The 6d5/2 Level Of Neutral 133Cs Using Two-Photon Spectroscopy, M. T. Herd, E. C. Cook, William Williams Oct 2021

Absolute Frequency Measurement Of The 6d5/2 Level Of Neutral 133Cs Using Two-Photon Spectroscopy, M. T. Herd, E. C. Cook, William Williams

Physics: Faculty Publications

We report absolute frequency measurements on the 6D5/2 level of neutral 133Cs using sub-Doppler two-photon spectroscopy. The absolute center-of-gravity energy for the 6D5/2 level is determined to be 22 631.683 877(6) cm−1, a factor of 170 times improvement over the previous measurement from 1964 of 22 631.6863(10) cm−1. This measurement also corrects a 2.4σ discrepancy with the previously measured value. The hyperfine coefficients were found to be A = −4.629(14) and B = −0.10(15) MHz, which are consistent with previous results.

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Absolute Frequency Measurement Of The Llevel Of Neutral Using Two-Photon Spectroscopy, M. T. Herd, E. C. Cook, William Williams Oct 2021

Absolute Frequency Measurement Of The Llevel Of Neutral Using Two-Photon Spectroscopy, M. T. Herd, E. C. Cook, William Williams

Physics: Faculty Publications

We report absolute frequency measurements on the level of neutral using sub-Doppler two-photon spectroscopy. The absolute center-of-gravity energy for the level is determined to be , a factor of 170 times improvement over the previous measurement from 1964 of . This measurement also corrects a discrepancy with the previously measured value. The hyperfine coefficients were found to be and , which are consistent with previous results.

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Python Routines For Low Temperature Resistive Thermometry In Magnetic Fields, Nathanael Fortune, Scott T. Hannahs, Julia Frothingham Jul 2021

Python Routines For Low Temperature Resistive Thermometry In Magnetic Fields, Nathanael Fortune, Scott T. Hannahs, Julia Frothingham

Physics: Faculty Publications

No abstract provided.

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Evolution Of Magnetic Field Induced Ordering In The Layered Quantum Heisenberg Triangular-Lattice Antiferromagnet Ba3 Cosb2 O9, Nathanael Alexander Fortune, Q. Huang, T. Hong, J. Ma, E. S. Choi, Scott T. Hannahs, Z. Y. Zhao, X. F. Sun, Y. Takano, H. D. Zhou May 2021

Evolution Of Magnetic Field Induced Ordering In The Layered Quantum Heisenberg Triangular-Lattice Antiferromagnet Ba3 Cosb2 O9, Nathanael Alexander Fortune, Q. Huang, T. Hong, J. Ma, E. S. Choi, Scott T. Hannahs, Z. Y. Zhao, X. F. Sun, Y. Takano, H. D. Zhou

Physics: Faculty Publications

Quantum fluctuations in the effective spin- 1/2 layered triangular-lattice quantum Heisenberg antiferromagnet Ba3CoSb2O9 lift the classical degeneracy of the antiferromagnetic ground state in magnetic field, producing a series of novel spin structures for magnetic fields applied within the crystallographic ab plane, including a celebrated collinear “up-up-down” spin ordering with magnetization equal to 1/3 of the saturation magnetization over an extended field range. Theoretically unresolved, however, are the effects of interlayer antiferromagnetic coupling and transverse magnetic fields on the ground states of this system. Additional magnetic field induced phase transitions are theoretically expected and in some …

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Complex Langevin And Other Approaches To The Sign Problem In Quantum Many-Body Physics, Casey E. Berger, L. Rammelmüller, A. C. Loheac, F. Ehmann, J. Braun, J. E. Drut Jan 2021

Complex Langevin And Other Approaches To The Sign Problem In Quantum Many-Body Physics, Casey E. Berger, L. Rammelmüller, A. C. Loheac, F. Ehmann, J. Braun, J. E. Drut

Physics: Faculty Publications

We review the theory and applications of complex stochastic quantization to the quantum many-body problem. Along the way, we present a brief overview of a number of ideas that either ameliorate or in some cases altogether solve the sign problem, including the classic reweighting method, alternative Hubbard–Stratonovich transformations, dual variables (for bosons and fermions), Majorana fermions, density-of-states methods, imaginary asymmetry approaches, and Lefschetz thimbles. We discuss some aspects of the mathematical underpinnings of conventional stochastic quantization, provide a few pedagogical examples, and summarize open challenges and practical solutions for the complex case. Finally, we review the recent applications of complex …

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Evolution Of Magnetic-Field-Induced Ordering In The Layered Structure Quantum Heisenberg Triangular-Lattice Antiferromagnet Ba3Cosb2O9, Nathanael Alexander Fortune, Q. Huang, T. Hong, J. Ma, E. S. Choi, S. T. Hannahs, Z. Y. Zhao, X. F. Sun, Y. Takano, H. D. Zhou Dec 2020

Evolution Of Magnetic-Field-Induced Ordering In The Layered Structure Quantum Heisenberg Triangular-Lattice Antiferromagnet Ba3Cosb2O9, Nathanael Alexander Fortune, Q. Huang, T. Hong, J. Ma, E. S. Choi, S. T. Hannahs, Z. Y. Zhao, X. F. Sun, Y. Takano, H. D. Zhou

Physics: Faculty Publications

Quantum fluctuations in the effective spin-1/2 layered structure triangular-lattice quantum Heisenberg antiferromagnet Ba3CoSb2O9 lift the classical degeneracy of the antiferromagnetic ground state in magnetic field, producing a series of novel spin structures for magnetic fields applied within the crystallographic ab plane, including a celebrated collinear ‘up-up-down’ spin ordering with magnetization equal to 1/3 of the saturation magnetization over an extended field range. Theoretically unresolved, however, are the effects of interlayer antferromagnetic coupling and transverse magnetic fields on the ground states of this system. Additional magnetic-field-induced phase transitions are theoretically expected and in some cases have …

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Vortex-Antivortex Physics In Shell-Shaped Bose-Einstein Condensates, Karmela Padavić, Kuei Sun, Courtney Lannert, Smitha Vishveshwara Oct 2020

Vortex-Antivortex Physics In Shell-Shaped Bose-Einstein Condensates, Karmela Padavić, Kuei Sun, Courtney Lannert, Smitha Vishveshwara

Physics: Faculty Publications

Shell-shaped hollow Bose-Einstein condensates (BECs) exhibit behavior distinct from their filled counterparts and have recently attracted attention due to their potential realization in microgravity settings. Here we study distinct features of these hollow structures stemming from vortex physics and the presence of rotation. We focus on a vortex-antivortex pair as the simplest configuration allowed by the constraints on superfluid flow imposed by the closed-surface topology. In the two-dimensional limit of an infinitesimally thin shell BEC, we characterize the long-range attraction between the vortex-antivortex pair and find the critical rotation speed that stabilizes the pair against energetically relaxing towards self-annihilation. In …

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Pulsed Triple Frequency Modulation For Frequency Stabilization And Control Of Two Lasers To An Optical Cavity, William Williams, Maria Teresa Herd, E. C. Cook Aug 2020

Pulsed Triple Frequency Modulation For Frequency Stabilization And Control Of Two Lasers To An Optical Cavity, William Williams, Maria Teresa Herd, E. C. Cook

Physics: Faculty Publications

We present a method to stabilize two lasers to an optical cavity using pulsed triple frequency modulation. The setup allows simultaneous Pound–Drever–Hall stabilization, as well as independent frequency control, while removing interference terms that limit the frequency scan range and allowing for smaller modulation depths. A review of single, dual, and triple frequency modulation is also presented in addition to a discussion of how to effectively turn pulsed triple frequency modulation into independent dual frequency modulation for each laser. This method would increase the scan range to half the free spectral range.

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Thermodynamics Of Rotating Quantum Matter In The Virial Expansion, Casey E. Berger, K. J. Morrell, J. E. Drut Aug 2020

Thermodynamics Of Rotating Quantum Matter In The Virial Expansion, Casey E. Berger, K. J. Morrell, J. E. Drut

Physics: Faculty Publications

We characterize the high-temperature thermodynamics of rotating bosons and fermions in two-dimensional (2D) and three-dimensional (3D) isotropic harmonic trapping potentials. We begin by calculating analytically the conventional virial coefficients bn for all n in the noninteracting case, as functions of the trapping and rotational frequencies. We also report on the virial coefficients for the angular momentum and associated moment of inertia. Using the bn coefficients, we analyze the deconfined limit (in which the angular frequency matches the trapping frequency) and derive explicitly the limiting form of the partition function, showing from the thermodynamic standpoint how both the 2D and 3D …

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Resonant Two-Photon Spectroscopy Of The 2s3d 1D2 Level Of Neutral 9Be, Eryn C. Cook, Alisha D. Vira, William Williams Apr 2020

Resonant Two-Photon Spectroscopy Of The 2s3d 1D2 Level Of Neutral 9Be, Eryn C. Cook, Alisha D. Vira, William Williams

Physics: Faculty Publications

We report an absolute frequency measurement of the 2s3d 1 D2 state in neutral 9Be using two-photon spectroscopy with a resonant intermediate state. The absolute center-of-gravity energy is determined to be 64 428.40 321(55) cm−1, a factor of 180 more precise than the previous experimental measurement. We also confirm our previous result for the energy of the intermediate 2s2p 1 P1 level. Precision is limited by unresolved hyperfine structure and the complications of performing resonant two-photon spectroscopy on an atomic beam. A three-level rate-equation analysis is presented to explore, and minimize, systematic uncertainties arising from small deviations of the angle …

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Third- And Fourth-Order Virial Coefficients Of Harmonically Trapped Fermions In A Semiclassical Approximation, K. J. Morrell, Casey E. Berger, J. E. Drut Dec 2019

Third- And Fourth-Order Virial Coefficients Of Harmonically Trapped Fermions In A Semiclassical Approximation, K. J. Morrell, Casey E. Berger, J. E. Drut

Physics: Faculty Publications

Using a leading-order semiclassical approximation, we calculate the third- A nd fourth-order virial coefficients of nonrelativistic spin-1/2 fermions in a harmonic trapping potential in arbitrary spatial dimensions, and as functions of temperature, trapping frequency, and coupling strength. Our simple, analytic results for the interaction-induced changes Δb3 and Δb4 agree qualitatively, and in some regimes quantitatively, with previous numerical calculations for the unitary limit of three-dimensional Fermi gases.

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Shell Potentials For Microgravity Bose–Einstein Condensates, N. Lundblad, R. A. Carollo, Courtney Lannert, M. J. Gold, X. Jiang, D. Paseltiner, N. Sergay, D. C. Aveline Dec 2019

Shell Potentials For Microgravity Bose–Einstein Condensates, N. Lundblad, R. A. Carollo, Courtney Lannert, M. J. Gold, X. Jiang, D. Paseltiner, N. Sergay, D. C. Aveline

Physics: Faculty Publications

Extending the understanding of Bose–Einstein condensate (BEC) physics to new geometries and topologies has a long and varied history in ultracold atomic physics. One such new geometry is that of a bubble, where a condensate would be confined to the surface of an ellipsoidal shell. Study of this geometry would give insight into new collective modes, self-interference effects, topology-dependent vortex behavior, dimensionality crossovers from thick to thin shells, and the properties of condensates pushed into the ultradilute limit. Here we propose to implement a realistic experimental framework for generating shell-geometry BEC using radiofrequency dressing of magnetically trapped samples. Such a …

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Catalysis Of Stark-Tuned Interactions Between Ultracold Rydberg Atoms, A. L. Win, William Williams, T. J. Carroll, C. I. Sukenik Sep 2018

Catalysis Of Stark-Tuned Interactions Between Ultracold Rydberg Atoms, A. L. Win, William Williams, T. J. Carroll, C. I. Sukenik

Physics: Faculty Publications

We have experimentally investigated a catalysis effect in the resonant energy transfer between ultracold 85Rb Rydberg atoms. We studied the time dependence of the process, 34p+34p→34s+35s, and observed an enhancement of 34s state population when 34d state atoms are added. We have also performed numerical model simulations, which are in qualitative agreement with experiment and indicate that the enhancement arises from a redistribution of p-state atoms due to the presence of the d-state atoms.

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Testing Quantum Electrodynamics In The Lowest Singlet State Of Neutral Beryllium-9, E. C. Cook, Alisha Daya Vira, E. Livernois, William Williams Aug 2018

Testing Quantum Electrodynamics In The Lowest Singlet State Of Neutral Beryllium-9, E. C. Cook, Alisha Daya Vira, E. Livernois, William Williams

Physics: Faculty Publications

We report spectroscopic results on the 2s2p1P1 state in neutral atomic beryllium-9. The absolute frequency for the center of gravity is determined to be 42 565.4501(13)  cm−1, a factor of 130 more precise than the previous experimental measurement. The result is in agreement with and a factor of 8 more precise than the current best theoretical estimate of 42 565.441(11)  cm−1, which was calculated including the effects of quantum electrodynamics. Because of the large natural linewidth of the transition, the hyperfine constants were not able to be extracted to high precision.

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Static And Dynamic Properties Of Shell-Shaped Condensates, Kuei Sun, Karmela Padavić, Frances Yang, Smitha Vishveshwara, Courtney Lannert Jul 2018

Static And Dynamic Properties Of Shell-Shaped Condensates, Kuei Sun, Karmela Padavić, Frances Yang, Smitha Vishveshwara, Courtney Lannert

Physics: Faculty Publications

Static, dynamic, and topological properties of hollow systems differ from those that are fully filled as a result of the presence of a boundary associated with an inner surface. Hollow Bose-Einstein condensates (BECs) naturally occur in various ultracold atomic systems and possibly within neutron stars but have hitherto not been experimentally realized in isolation on Earth because of gravitational sag. Motivated by the expected first realization of fully closed BEC shells in the microgravity conditions of the Cold Atomic Laboratory aboard the International Space Station, we present a comprehensive study of spherically symmetric hollow BECs as well as the hollowing …

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Physics Of Hollow Bose-Einstein Condensates, Karmela Padavić, Kuei Sun, Courtney Lannert, Smitha Vishveshwara Jan 2018

Physics Of Hollow Bose-Einstein Condensates, Karmela Padavić, Kuei Sun, Courtney Lannert, Smitha Vishveshwara

Physics: Faculty Publications

Bose-Einstein condensate shells, while occurring in ultracold systems of coexisting phases and potentially within neutron stars, have yet to be realized in isolation on Earth due to the experimental challenge of overcoming gravitational sag. Motivated by the expected realization of hollow condensates by the space-based Cold Atomic Laboratory in microgravity conditions, we study a spherical condensate undergoing a topological change from a filled sphere to a hollow shell. We argue that the collective modes of the system show marked and robust signatures of this hollowing transition accompanied by the appearance of a new boundary. In particular, we demonstrate that the …

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Interacting Bosons At Finite Angular Momentum Via Complex Langevin, Casey E. Berger, Joaquín E. Drut Jan 2018

Interacting Bosons At Finite Angular Momentum Via Complex Langevin, Casey E. Berger, Joaquín E. Drut

Physics: Faculty Publications

Quantum field theories with a complex action suffer from a sign problem in stochastic nonpertur-bative treatments, making many systems of great interest – such as polarized or mass-imbalanced fermions and QCD at finite baryon density – extremely challenging to treat numerically. Another such system is that of bosons at finite angular momentum; experimentalists have successfully achieved vortex formation in ultracold bosonic atoms, and have measured quantities of interest such as density profiles and the moment of inertia. However, the treatment of superfluids requires the use of complex bosons, making the usual numerical methods unusable. In this work, we apply complex …

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Calorimetric Measurements Of Magnetic-Field-Induced Inhomogeneous Superconductivity Above The Paramagnetic Limit, Charles C. Agosta, Nathanael Alexander Fortune, Scott T. Hannahs, Shuyao Gu, Lucy Liang, Ju-Hyun Park, John A. Schleuter Jun 2017

Calorimetric Measurements Of Magnetic-Field-Induced Inhomogeneous Superconductivity Above The Paramagnetic Limit, Charles C. Agosta, Nathanael Alexander Fortune, Scott T. Hannahs, Shuyao Gu, Lucy Liang, Ju-Hyun Park, John A. Schleuter

Physics: Faculty Publications

We report the first magnetocaloric and calorimetric observations of a magnetic-field-induced phase transition within a superconducting state to the long-sought exotic Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconducting state, first predicted over 50 years ago. Through the combination of bulk thermodynamic calorimetric and magnetocaloric measurements in the organic superconductor κ−(BEDT−TTF)2Cu(NCS)2 as a function of temperature, magnetic field strength, and magnetic field orientation, we establish for the first time that this field-induced first-order phase transition at the paramagnetic limit Hp is a transition to a higher-entropy superconducting phase, uniquely characteristic of the FFLO state. We also establish that this high-field superconducting state displays the bulk …

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Magnetic-Field-Induced 1st Order Transition To Fflo State At Paramagnetic Limit In 2d Superconductors, Nathanael Alexander Fortune, C. C. Agosta, S. T. Hannahs, J. A. Schleuter Jan 2017

Magnetic-Field-Induced 1st Order Transition To Fflo State At Paramagnetic Limit In 2d Superconductors, Nathanael Alexander Fortune, C. C. Agosta, S. T. Hannahs, J. A. Schleuter

Physics: Faculty Publications

We have recently reported the first direct calorimetric observation of a magnetic-field-induced first-order phase transition into a high-field FFLO superconducting state at the Clogston-Chandrasekar ‘Pauli’ paramagnetic limitHp in a 2D superconductor κ − (BEDT-TTF)2Cu(NCS)2. The high-field state is both higher entropy and strongly paramagnetic, as thermodynamically required for the FFLO state. Here we compare our results with theoretical predictions for the field dependence of the high-field FFLO state in the 2D limit, revealing tentative evidence for transitions between FFLO states of differing order parameter. We also present calorimetric evidence for a 1st order phase transition into the FFLO state for …

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Hard-Wall And Non-Uniform Lattice Monte Carlo Approaches To One-Dimensional Fermi Gases In A Harmonic Trap, Casey E. Berger, Joaquín E. Drut, William J. Porter Nov 2016

Hard-Wall And Non-Uniform Lattice Monte Carlo Approaches To One-Dimensional Fermi Gases In A Harmonic Trap, Casey E. Berger, Joaquín E. Drut, William J. Porter

Physics: Faculty Publications

We present in detail two variants of the lattice Monte Carlo method aimed at tackling systems in external trapping potentials: a uniform-lattice approach with hard-wall boundary conditions, and a non-uniform Gauss–Hermite lattice approach. Using those two methods, we compute the ground-state energy and spatial density profile for systems of N=4–8 harmonically trapped fermions in one dimension. From the favorable comparison of both energies and density profiles (particularly in regions of low density), we conclude that the trapping potential is properly resolved by the hard-wall basis. Our work paves the way to higher dimensions and finite temperature analyses, as calculations with …

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Harmonically Trapped Fermions In Two Dimensions: Ground-State Energy And Contact Of Su(2) And Su(4) Systems Via A Nonuniform Lattice Monte Carlo Method, Zhihuan Luo, Casey E. Berger, Joaquín E. Drut Mar 2016

Harmonically Trapped Fermions In Two Dimensions: Ground-State Energy And Contact Of Su(2) And Su(4) Systems Via A Nonuniform Lattice Monte Carlo Method, Zhihuan Luo, Casey E. Berger, Joaquín E. Drut

Physics: Faculty Publications

We study harmonically trapped, unpolarized fermion systems with attractive interactions in two spatial dimensions with spin degeneracies Nf=2 and 4 and N/Nf=1,3,5, and 7 particles per flavor. We carry out our calculations using our recently proposed quantum Monte Carlo method on a nonuniform lattice. We report on the ground-state energy and contact for a range of couplings, as determined by the binding energy of the two-body system, and show explicitly how the physics of the Nf-body sector dominates as the coupling is increased.

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Can The Wave Function In Configuration Space Be Replaced By Single-Particle Wave Functions In Physical Space?, Travis Norsen, Damiano Marian, Xavier Oriols Oct 2015

Can The Wave Function In Configuration Space Be Replaced By Single-Particle Wave Functions In Physical Space?, Travis Norsen, Damiano Marian, Xavier Oriols

Physics: Faculty Publications

The ontology of Bohmian mechanics includes both the universal wave function (living in 3N-dimensional configuration space) and particles (living in ordinary 3-dimensional physical space). Proposals for understanding the physical significance of the wave function in this theory have included the idea of regarding it as a physically-real field in its 3N-dimensional space, as well as the idea of regarding it as a law of nature. Here we introduce and explore a third possibility in which the configuration space wave function is simply eliminated – replaced by a set of single-particle pilot-wave fields living in ordinary physical space. Such a re-formulation …

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Energy, Contact, And Density Profiles Of One-Dimensional Fermions In A Harmonic Trap Via Nonuniform-Lattice Monte Carlo Calculations, Casey E. Berger, E. R. Anderson, J. E. Drut May 2015

Energy, Contact, And Density Profiles Of One-Dimensional Fermions In A Harmonic Trap Via Nonuniform-Lattice Monte Carlo Calculations, Casey E. Berger, E. R. Anderson, J. E. Drut

Physics: Faculty Publications

We determine the ground-state energy and Tan's contact of attractively interacting few-fermion systems in a one-dimensional harmonic trap, for a range of couplings and particle numbers. Complementing those results, we show the corresponding density profiles. The calculations were performed with a lattice Monte Carlo approach based on a nonuniform discretization of space, defined via Gauss-Hermite quadrature points and weights. This particular coordinate basis is natural for systems in harmonic traps, and can be generalized to traps of other shapes. In all cases, it yields a position-dependent coupling and a corresponding nonuniform Hubbard-Stratonovich transformation. The resulting path integral is performed with …

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Are There Really Two Different Bell’S Theorems?, Travis Norsen Mar 2015

Are There Really Two Different Bell’S Theorems?, Travis Norsen

Physics: Faculty Publications

This is a polemical response to Howard Wiseman’s recent paper, “The two Bell’s theorems of John Bell”. Wiseman argues that, in 1964, Bell established a conflict between the quantum mechanical predictions and the joint assumptions of determinism and (what is now usually known as) “parameter independence”. Only later, in 1976, did Bell, according to Wiseman, first establish a conflict between the quantum mechanical predictions and locality alone (in the specific form that Bell would sometimes call “local causality”). Thus, according to Wiseman, the long-standing disagreements about what, exactly, Bell’s theorem does and does not prove can be understood largely as …

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Weak Measurement And Bohmian Conditional Wave Functions, Travis Norsen Nov 2014

Weak Measurement And Bohmian Conditional Wave Functions, Travis Norsen

Physics: Faculty Publications

It was recently pointed out (and demonstrated experimentally) by Lundeen et al. that the wave function of a particle (more precisely, the wave function possessed by each member of an ensemble of identically-prepared particles) can be "directly measured" using weak measurement. Here it is shown that if this same technique is applied, with appropriate post-selection, to one particle from a (perhaps entangled) multi-particle system, the result is precisely the so-called "conditional wave function" of Bohmian mechanics. Thus, a plausibly operationalist method for defining the wave function of a quantum mechanical sub-system corresponds to the natural definition of a sub-system wave …

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Magnetic-Field-Induced Heisenberg To Xy Crossover In A Quasi-2d Quantum Antiferromagnet, Nathanael Alexander Fortune, Scott T. Hannahs, C. P. Landee, M. M. Turnbull, F. Xiao Jan 2014

Magnetic-Field-Induced Heisenberg To Xy Crossover In A Quasi-2d Quantum Antiferromagnet, Nathanael Alexander Fortune, Scott T. Hannahs, C. P. Landee, M. M. Turnbull, F. Xiao

Physics: Faculty Publications

The magnetic-field-dependent ordering temperature of the quasi-2D quantum Heisenberg antiferromagnet (QHAF) Cu(pz)2(ClO4)2 was determined by calorimetric measurement in applied dc fields up to 33 tesla. The magnetic phase diagram shows a round maximum at 5.95 K and 17.5 T (at ≈ 1/3 of its saturation field), a 40 percent enhancement of the ordering temperature above the zero field value of 4.25 K. The enhancement and reentrance are consistent with predictions of a field-induced Heisenberg to XY crossover behavior for an ideal 2D QHAF system.

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