Physics Commons^™

Gravitationally Induced Quantum Superposition Reduction With Large Extra Dimensions, Jonas R. Mureika

Jonas Mureika

A gravity-driven mechanism (``objective reduction'') proposed to explain quantum state reduction is analyzed in light of the possible existence of large extra dimensions in the ADD scenario. By calculating order-of-magnitude estimates for nucleon superpositions, it is shown that if the mechanism at question is correct, constraints may be placed on the number and size of extra dimensions. Hence, measurement of superposition collapse times ({\it e.g.} through diffraction or reflection experiments) could represent a new probe of extra dimensions. The influence of a time-dependent gravitational constant on the gravity-driven collapse scheme with and without the presence of extra dimensions is also …

Sub-Planckian Black Holes And The Generalized Uncertainty Principle, Bernard Carr, Jonas R. Mureika, Piero Nicolini

Jonas Mureika

The Black Hole Uncertainty Principle correspondence suggests that there could exist black holes with mass beneath the Planck scale but radius of order the Compton scale rather than Schwarzschild scale. We present a modified, self-dual Schwarzschild-like metric that reproduces desirable aspects of a variety of disparate models in the sub-Planckian limit, while remaining Schwarzschild in the large mass limit. The self-dual nature of this solution under M ↔ M−1 naturally implies a Generalized Uncertainty Principle with the linear form Δx∼1/Δp+Δp. We also demonstrate a natural dimensional reduction feature, in that the gravitational radius and thermodynamics of sub-Planckian objects resemble that …

Aspects Of Noncommutative (1+1)-Dimensional Black Holes, Jonas R. Mureika, Piero Nicolini

Jonas Mureika

We present a comprehensive analysis of the spacetime structure and thermodynamics of ( 1 + 1 )-dimensional black holes in a noncommutative framework. It is shown that a wider variety of solutions are possible than the commutative case considered previously in the literature. As expected, the introduction of a minimal length √ θ cures singularity pathologies that plague the standard two-dimensional general relativistic case, where the latter solution is recovered at large length scales. Depending on the choice of input parameters (black hole mass M, cosmological constant Λ , etc.), black hole solutions with zero, up to six, horizons are …

Fractal Dimensions In Perceptual Color Space: A Comparison Study Using Jackson Pollock’S Art, Jonas R. Mureika

Jonas Mureika

The fractal dimensions of color-specific paint patterns in various Jackson Pollock paintings are calculated using a filtering process that models perceptual response to color differences (L*a*b* color space). The advantage of the L*a*b* space filtering method over traditional red-green-blue (RGB) spaces is that the former is a perceptually uniform (metric) space, leading to a more consistent definition of “perceptually different” colors. It is determined that the RGB filtering method underestimates the perceived fractal dimension of lighter-colored patterns but not of darker ones, if the same selection criteria is applied to each. Implications of the findings to Fechner’s “principle of …

Constraints On Vector Unparticle Physics From Cosmic Censorship, Jonas R. Mureika

Jonas Mureika

Vector unparticle couplings to standard model fields produce repulsive corrections to gravity. From a general relativistic perspective, this leads to an effective Reissner-Nordstrom-like metric whose "charge" is a function of the unparticle coupling constant λ, and therefore can admit naked singularities. Requiring the system to respect cosmic censorship provides a new method of constraining the value of λ. These limits are extremely loose for stellar-mass black holes, but commensurate with existing bounds for primordial black holes. In the case of theoretical low-mass black holes, the bounds on λ are much stricter than those derived from astrophysical and accelerator phenomenology. Additional …

(1+1)-Dimensional Entropic Gravity, R. B. Mann, Jonas R. Mureika

Jonas Mureika

We consider the formulation of entropic gravity in two spacetime dimensions. The usual gravitational force law is derived even in the absence of area, as normally required by the holographic principle. A special feature of this perspective concerns the nature of temperature and entropy defined at a point. We argue that the constancy of the gravitational force in one spatial dimension implies the information contained at each point in space is an internal degree of freedom on the manifold, and furthermore is a universal constant, contrary to previous assertions that entropic gravity in one spatial dimension is ill-defined. We give …

Detecting Vanishing Dimensions Via Primordial Gravitational Wave Astronomy, Jonas R. Mureika, Dejan Stojkovic

Jonas Mureika

Lower dimensionality at higher energies has manifold theoretical advantages as recently pointed out by Anchordoqui et al. [arXiv:1003.5914]. Moreover, it appears that experimental evidence may already exist for it: A statistically significant planar alignment of events with energies higher than TeV has been observed in some earlier cosmic ray experiments. We propose a robust and independent test for this new paradigm. Since ( 2 + 1 )-dimensional spacetimes have no gravitational degrees of freedom, gravity waves cannot be produced in that epoch. This places a universal maximum frequency at which primordial waves can propagate, marked by the transition between dimensions. …

Could Any Black Holes Be Produced At The Lhc?, Jonas R. Mureika, Piero Nicolini, Euro Spallucci

Jonas Mureika

We introduce analytical quantum gravity modifications of the production cross section for terascale black holes by employing an effective ultraviolet cut off l. We find the new cross sections approach the usual "black disk" form at high energy, while they differ significantly near the fundamental scale from the standard increase with respect to s. We show that the heretofore discontinuous step function used to represent the cross section threshold can realistically be modeled by two functions representing the incoming and final parton states in a high energy collision. The growth of the cross section with collision energy is …

"Blinded By The Lines: Mid-Ir Spectra Of Mira Variables Taken With Spitzer", Dana Baylis-Aguirre, Michelle J. Creech-Eakman, Donald G. Luttermoser, Tina Gueth

Donald G. Luttermoser

We present preliminary analysis of mid-infrared spectra of M-type and C-type Mira variables. Due to the brightness of this sample, it is straightforward to monitor changes with phase in the infrared spectral features of these regular pulsators. We have spectra of 25 Mira variables, taken with phase, using the Spitzer Infrared Spectrograph (IRS) high-resolution module. Each star has multiple spectra obtained over a one-year period from 2008-09. This is a rich, unique data set due to multiple observations of each star and the high signal-to-noise ratio from quick exposure times to prevent saturation of the IRS instrument. This paper focuses …

Physical Mechanisms Leading To The Coulomb Blockade And Coulomb Staircase Structures In Strongly Coupled Multi-Island Single-Electron Devices, Madhusudan A. Savaikar, Paul L. Bergstrom, John A. Jaszczak

Paul Bergstrom

Controlled transport of electrons through tunnel junctions and their confinement by mesoscopic structures have opened up immense possibilities of single-electron device (SED) applications. The realization of a practical working SED has remained challenging largely owing to the poor understanding of the physics of operation of singe-electron tunneling devices, especially of those with multiple nanometer-sized islands. In this simulation study of one-dimensional (1D) multi-island chains, we propose physical mechanisms that lead to the coulomb blockade (CB) and coulomb staircase (CS) characteristics that are enhanced by the geometrical disorder in the chain. With increasing source-drain (VDS = VD − VS) bias, a …

New Flexible Channels For Room Temperature Tunneling Field Effect Transistors, Boyi Hao, Anjana Asthana, Paniz Khanmohammadi, Paul Bergstrom, Douglas R. Banyai, Madhusudan A. Savaikar, John A. Jaszczak, Yoke Khin Yap

Paul Bergstrom

Tunneling field effect transistors (TFETs) have been proposed to overcome the fundamental issues of Si based transistors, such as short channel effect, finite leakage current, and high contact resistance. Unfortunately, most if not all TFETs are operational only at cryogenic temperatures. Here we report that iron (Fe) quantum dots functionalized boron nitride nanotubes (QDs-BNNTs) can be used as the flexible tunneling channels of TFETs at room temperatures. The electrical insulating BNNTs are used as the one-dimensional (1D) substrates to confine the uniform formation of Fe QDs on their surface as the flexible tunneling channel. Consistent semiconductor-like transport behaviors under various …

Simulation Of Charge Transport In Multi-Island Tunneling Devices: Application To Disordered One-Dimensional Systems At Low And High Biases, Madhusudan A. Savaikar, Douglas R. Banyai, Paul Bergstrom, John A. Jaszczak

Paul Bergstrom

Although devices have been fabricated displaying interesting single-electron transport characteristics, there has been limited progress in the development of tools that can simulate such devices based on their physical geometry over a range of bias conditions up to a few volts per junction. In this work, we present the development of a multi-island transport simulator, MITS, a simulator of tunneling transport in multi-island devices that takes into account geometrical and material parameters, and can span low and high source-drain biases. First, the capabilities of MITS are demonstrated by modeling experimentaldevices described in the literature, and showing that the simulated device …

Evaluation Of Commercial Nickel–Phosphorus Coating For Ultracold Neutron Guides Using A Pinhole Bottling Method, Robert W. Pattie, Evan R. Adamek, T. Brenner, A. Brandt, Leah J. Broussard, Nathan Callahan, Stephen M. Clayton, Chris Cude-Woods, Scott A. Currie, Peter Geltenbort, Takeyasu M. Ito, T. Lauer, Chenyu Liu, Jaroslaw Majewski, Mark F. Makela, Yasuhiro Masuda, Christopher L. Morris, John C. Ramsey, Daniel J. Salvat, Alexander Saunders, Juri Schroffenegger, Zebo Tang, Wanchun Wei, Zhehui Wang, Erik B. Watkins, Albert R. Young, B.A. Zeck

Robert W. Pattie Jr.

The First Open-Source General Relativistic Force-Free Electrodynamics Code, Maria Babiuc-Hamilton, Zach Etienne, Mew-Bing Wan

Maria C. Babiuc-Hamilton

We are writing the first open-source, general relativistic force-free electrodynamics code: GiRaFFE. The goal is to numerically simulate neutron star and black hole magnetospheres. The GiRaFFE is alive! It has passed a number of 1D code validation tests, and 3D tests are underway. We plan to release the code and test suite initial data routines open-source to the community.

Towards A Standardized Characteristic Extraction Tool, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Knowing the precise details of the gravitational wave signature obtained from numerical simulations of binary black hole mergers is a key requirement for meaningful detection and scientific interpretation of the data. However, the waveforms are not easy to be accurately computed. The importance of this problem to the future of gravitational wave astronomy is well recognized. Cauchy-Characteristic Extraction (CCE) is the most precise and refined extraction method available. The CCE technique connects the strong-field Cauchy evolution of the spacetime near the merger to the characteristic evolution to future null infinity where the waveform is extracted in an unambiguous way. Recently, …

Simulating Magnetospheres With Numerical Relativity: The Giraffe Code, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Numerical Relativity is successful in the simulation of black holes and gravitational waves. In recent years, teams have tackled the problem of the interaction of gravitational and electromagnetic waves. We developed a new code for the numerical simulation of neutron and black hole magnetospheres, using the FFE formalism. We tested the performance of the new code named GiRaFFE, in 1D and 3D test suits. We will study magnetospheres, focusing on jets by the Blandford -Znajek mechanism.

Cauchy-Characteristic Patching With Improved Accuracy, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Cauchy-characteristic extractions (CCE) avoids the errors due to extraction at finite worldtube. The Cauchy and the characteristic approaches have complementary strengths and weaknesses. Unification of the two methods is a promising way of combining the strengths of both formalisms.

Towards A Fully Nonlinear Cauchy Characteristic Extraction, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

The artificial finite outer boundary present in Cauchy codes introduce two sources of error: The outer boundary condition and waveform extraction at an inner worldtube. The problem of proper boundary condition for a radiating system can be solved only by extension to Ι+ (conformal compactification). Cauchy Characteristic Extraction (CCE) offers a means to avoid these errors.

Towards Improved Accuracy Of Gravitational Waves Extraction, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Results in developing two new methods to improve the accuracy of waveform extraction using characteristic evolution. Numerical method: circular boundaries, with angular dissipation in the characteristic code. Geometric method: computation of Weyl tensor component Y4 at null infinity, in a conformally compactified treatment. Comparison and calibration in tests problems based upon linearized waves.

Gravitational & Electromagnetic Waves On The Null Cone, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Bondi (1962) proved mathematically the existence of gravitational waves at null infinity. He found an exact solution of Einstein equations. Within this metric, he calculated the loss of mass due to the emission of gravitational waves. The mas of a system is constant if and only if there is no news. If there is news, the mass decreases as long as there are news.

Testing A Model For The Well-Posedness Of The Cauchy-Characteristic Problem In Bondi Coordinates, Maria Babiuc-Hamilton, Jeff Winicour

Maria C. Babiuc-Hamilton

Gravity waves reveal colliding black holes, galaxies, the birth of a black hole in a supernova and the growth pains of our universe. Gravitational waves are unambiguous measured only at future null infinity.

Steps Towards A Nonlinear Cauchy-Characteristic Code Patching, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Cauchy-characteristic extractions (CCE) avoids the errors due to extraction at finite worldtube. The Cauchy and the characteristic approaches have complementary strengths and weaknesses. Unification of the two methods is a promising way of combining the strengths of both formalisms.

Characteristics Of Gravitational And Electromagnetic Radiation, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Gravitational waves from the early universe are detectable, but detection is difficult. The strain is extremely small of magnitude 10-3 the width of a proton. There are detection and computational challenges.

An Analysis Of The Gravitational Waves Null Memory, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Gravitational wave astronomy sees (hears) gravitational waves by observing the phenomena of gravitational and electromagnetic memory, and the formation of trapped surfaces and horizons.

Tools For Gravitational Wave Astronomy, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Gravitational waves have been confirmed. Tools are available for their study, including the Einstein Toolkit, SimulationTools and the SXS Gravitational Waveform Database.

Gravity & Electromagnetism On The Null Cone, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Gravitational and electromagnetic radiation travel along light rays, which are principal null directions in space-time. They are characteristic surfaces of Einstein and Maxwell equations. In characteristic coordinates, the field is described by ordinary differential equations.

A New Algorithm For The Numerical Computation Of Gravitational Waves, Maria Babiuc-Hamilton, Jeff Winicour

Maria C. Babiuc-Hamilton

With gravitational waves, Gravitational Wave Astronomy can “see” colliding back holes and galaxies, the birth of a black hole in a supernova, the growth pains of our universe and the structure of spacetime.

A Hyperbolic Solver For Black Hole Initial Data In Numerical Relativity, Maria Babiuc-Hamilton, Jeff Winicour, I. Racz

Maria C. Babiuc-Hamilton

Initial data in numerical relativity. The constraints are formulated as elliptic equations, parabolic equations and strongly hyperbolic equations. This presentation is about a different approach to initial data for black holes, the strongly hyperbolic method.

Impulse-Momentum Diagrams, David Rosengrant

David Rosengrant

Multiple representations are a valuable tool to help students learn and understand physics concepts. Furthermore, representations help students learn how to think and act like real scientists. These representations include: pictures, free‐body diagrams, energy bar charts, electrical circuits, and, more recently, computer simulations and animations. However, instructors have limited choices when they want to help their students understand impulse and momentum. One of the only available options is the impulse‐momentum bar chart. The bar charts can effectively show the magnitude of the momentum as well as help students understand conservation of momentum, but they do not easily show the actual …

Following Student Gaze Patterns In Physical Science Lectures, David Rosengrant, Doug Hearrington, Kerriann Alvarado, Danielle Keeble

David Rosengrant

This study investigates the gaze patterns of undergraduate college students attending a lecture-based physical science class to better understand the relationships between gaze and focus patterns and student attention during class. The investigators used a new eye-tracking product; Tobii Glasses. The glasses eliminate the need for subjects to focus on a computer screen or carry around a backpack-sized recording device, thus giving an investigator the ability to study a broader range of research questions. This investigation includes what students focus on in the classroom (i.e. demonstrations, instructor, notes, board work, and presentations) during a normal lecture, what diverts attention away …