2,782 research outputs found
Simulating lattice gauge theories on a quantum computer
We examine the problem of simulating lattice gauge theories on a universal
quantum computer. The basic strategy of our approach is to transcribe lattice
gauge theories in the Hamiltonian formulation into a Hamiltonian involving only
Pauli spin operators such that the simulation can be performed on a quantum
computer using only one and two qubit manipulations. We examine three models,
the U(1), SU(2), and SU(3) lattice gauge theories which are transcribed into a
spin Hamiltonian up to a cutoff in the Hilbert space of the gauge fields on the
lattice. The number of qubits required for storing a particular state is found
to have a linear dependence with the total number of lattice sites. The number
of qubit operations required for performing the time evolution corresponding to
the Hamiltonian is found to be between a linear to quadratic function of the
number of lattice sites, depending on the arrangement of qubits in the quantum
computer. We remark that our results may also be easily generalized to higher
SU(N) gauge theories.Comment: 15 pages, 4 figures, 3 table
Scale dependence of in N-flation
Adopting the horizon-crossing approximation, we derive the spectral index of
in general N-flation model. Axion N-flation model is taken as a
typical model for generating a large which characterizes the size of
local form bispectrum. We find that its tilt is negligibly small
when all inflatons have the same potential, but a negative detectable
can be achieved in the axion N-flation with different decay
constants for different inflatons. The measurement of can be used
to support or falsify the axion N-flation in the near future.Comment: 15 pages, 2 figures; a subsection with detectable scale dependence of
f_NL added; more discussions added and version accepted for publication in
JCA
Sleep disturbance and serum ferritin levels associate with high impulsivity and impulse control disorders in male Parkinson\u27s Disease patients
Impulse control disorders (ICDs) occur in a subset of Parkinson’s disease (PD) patients on dopaminergic medications however there are currently no reliable markers to identify patients at risk. Sleep disturbances are more common in patients with an ICD. Serum ferritin levels have been associated with PD disease stage and progression, but have not previously been associated with impulsivity levels. The objective of this study was to determine if serum ferritin levels and sleep disturbance are associated with high traits of impulsivity and ICD in a cohort of PD patients attending a movement disorders clinic. This study assessed impulsiveness in 87 PD patients using the Barratt Impulsiveness Scale. Severity of sleep disturbance was determined using the sleep-related items of the MDS-UPDRS. Serum ferritin, iron and transferrin levels were measured in patients, as well as 36 age-matched healthy controls. Serum ferritin levels were significantly elevated in male PD patients in the high impulsivity group compared to patients in the low (p=.022) and normal range groups (p=.024) and showed a linear increase across the three groups. Sleep disturbance also demonstrated a linear trend, which was most severe in the high impulsivity group (p=.030). A subgroup of 11 male PD patients who fulfilled the DSM-5 criteria for an ICD had significantly higher ferritin levels and more severe sleep disturbance when compared with the remaining male PD cohort. Serum ferritin levels and sleep disturbance severity are highlighted as potential markers for abnormal impulsivity and ICD in PD patients
Inhomogeneous non-Gaussianity
We propose a method to probe higher-order correlators of the primordial
density field through the inhomogeneity of local non-Gaussian parameters, such
as f_NL, measured within smaller patches of the sky. Correlators between
n-point functions measured in one patch of the sky and k-point functions
measured in another patch depend upon the (n+k)-point functions over the entire
sky. The inhomogeneity of non-Gaussian parameters may be a feasible way to
detect or constrain higher-order correlators in local models of
non-Gaussianity, as well as to distinguish between single and multiple-source
scenarios for generating the primordial density perturbation, and more
generally to probe the details of inflationary physics.Comment: 16 pages, 2 figures; v2: Minor changes and references added. Matches
the published versio
Quantum simulator for the Hubbard model with long-range Coulomb interactions using surface acoustic waves
A practical experimental scheme for a quantum simulator of strongly
correlated electrons is proposed. Our scheme employs electrons confined in a
two dimensional electron gas in a GaAs/AlGaAs heterojunction. Two surface
acoustic waves are then induced in the GaAs substrate, which create a two
dimensional ``egg-carton'' potential. The dynamics of the electrons in this
potential is described by a Hubbard model with long-range Coulomb interactions.
The state of the electrons in this system can be probed via its conductance and
noise properties. This allows the identification of a metallic or insulating
state. Numerical estimates for the parameters appearing in the effective
Hubbard model are calculated using the proposed experimental system. These
calculations suggest that observations of quantum phase transition phenomena of
the electrons in the potential array are within experimental reach.Comment: 5 pages, 5 figure
Extended Timed Up and Go assessment as a clinical indicator of cognitive state in Parkinson\u27s disease
Objective: To evaluate a modified extended Timed Up and Go (extended-TUG) assessment against a panel of validated clinical assessments, as an indicator of Parkinson’s disease (PD) severity and cognitive impairment.
Methods: Eighty-seven participants with idiopathic PD were sequentially recruited from a Movement Disorders Clinic. An extended-TUG assessment was employed which required participants to stand from a seated position, walk in a straight line for 7 metres, turn 180 degrees and then return to the start, in a seated position. The extended-TUG assessment duration was correlated to a panel of clinical assessments, including the Unified Parkinson’s Disease Rating Scale (MDS-UPDRS), Quality of Life (PDQ-39), Scales for Outcomes in Parkinson’s disease (SCOPA-Cog), revised Addenbrooke’s Cognitive Index (ACE-R) and Barratt’s Impulsivity Scale 11 (BIS-11).
Results: Extended-TUG time was significantly correlated to MDS-UPDRS III score and to SCOPA-Cog, ACE-R (p\u3c0.001) and PDQ-39 scores (p\u3c0.01). Generalized linear models determined the extended-TUG to be a sole variable in predicting ACE-R or SCOPA-Cog scores. Patients in the fastest extended-TUG tertile were predicted to perform 8.3 and 13.4 points better in the SCOPA-Cog and ACE-R assessments, respectively, than the slowest group. Patients who exceeded the dementia cut-off scores with these instruments exhibited significantly longer extended-TUG times.
Conclusions: Extended-TUG performance appears to be a useful indicator of cognition as well as motor function and quality of life in PD, and warrants further evaluation as a first line assessment tool to monitor disease severity and response to treatment. Poor extended-TUG performance may identify patients without overt cognitive impairment form whom cognitive assessment is needed
Criminal Law-Involuntary Manslaughter- Presence as a Pre-Requisite to Liablity for Permitting an Incompetent to Drive an Automobile
Defendant gave his car keys to an intoxicated friend and permitted him to operate the vehicle while the defendant was at home in bed. As he was driving on the wrong side of the highway, the friend was involved in a head-on collision which resulted in the death of the drivers of both vehicles. Defendant was convicted of involuntary manslaughter and of the misdemeanor of allowing an intoxicated person to operate his automobile. On appeal, held, conviction of manslaughter reversed. Although one who permits an intoxicated person to drive his car is guilty of a misdemeanor, he cannot be held liable for involuntary manslaughter unless he is present at the time of the fatal event. People v. Marshall, 362 Mich. 170, 106 N.W.2d 842 (1961)
Quantum simulation of Fermi-Hubbard models in semiconductor quantum dot arrays
We propose a device for studying the Fermi-Hubbard model with long-range
Coulomb interactions using an array of quantum dots defined in a semiconductor
two-dimensional electron gas system. Bands with energies above the lowest
energy band are used to form the Hubbard model, which allows for an
experimentally simpler realization of the device. We find that depending on
average electron density, the system is well described by a one- or two-band
Hubbard model. Our device design enables the control of the ratio of the
Coulomb interaction to the kinetic energy of the electrons independently to the
filling of the quantum dots, such that a large portion of the Hubbard phase
diagram may be probed. Estimates of the Hubbard parameters suggest that a
metal-Mott insulator quantum phase transition and a d-wave superconducting
phase should be observable using current fabrication technologies.Comment: 12 pages, 3 figures, 1 table
Scale-dependent non-Gaussianity probes inflationary physics
We calculate the scale dependence of the bispectrum and trispectrum in
(quasi) local models of non-Gaussian primordial density perturbations, and
characterize this scale dependence in terms of new observable parameters. They
can help to discriminate between models of inflation, since they are sensitive
to properties of the inflationary physics that are not probed by the standard
observables. We find consistency relations between these parameters in certain
classes of models. We apply our results to a scenario of modulated reheating,
showing that the scale dependence of non-Gaussianity can be significant. We
also discuss the scale dependence of the bispectrum and trispectrum, in cases
where one varies the shape as well as the overall scale of the figure under
consideration. We conclude providing a formulation of the curvature
perturbation in real space, which generalises the standard local form by
dropping the assumption that f_NL and g_NL are constants.Comment: 27 pages, 2 figures. v2: Minor changes to match the published versio
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