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Articles 1 - 30 of 108
Full-Text Articles in Physics
Newtonian Fractional-Dimension Gravity And Disk Galaxies, Gabriele U. Varieschi
Newtonian Fractional-Dimension Gravity And Disk Galaxies, Gabriele U. Varieschi
Physics Faculty Works
This paper continues previous work on a possible alternative model of gravity, based on the theory of fractional-dimension spaces applied to Newton's law of gravitation. In particular, our Newtonian Fractional-Dimension Gravity (NFDG) is now applied to axially-symmetric stellar structures, such as thin/thick disk galaxies described by exponential, Kuzmin, or other similar mass distributions. As in the case of spherically-symmetric structures, which was studied in previous work on the subject, we examine a possible connection between NFDG and Modified Newtonian Dynamics (MOND), a leading alternative gravity model, which accounts for the observed properties of galaxies and other astrophysical structures without requiring …
Newtonian Fractional-Dimension Gravity And Mond, Gabriele U. Varieschi
Newtonian Fractional-Dimension Gravity And Mond, Gabriele U. Varieschi
Physics Faculty Works
This paper introduces a possible alternative model of gravity based on the theory of fractional-dimension spaces and its applications to Newtonian gravity. In particular, Gauss’s law for gravity as well as other fundamental classical laws are extended to a D-dimensional metric space, where D can be a non-integer dimension. We show a possible connection between this Newtonian Fractional-Dimension Gravity (NFDG) and Modified Newtonian Dynamics (MOND), a leading alternative gravity model which accounts for the observed properties of galaxies and other astrophysical structures without requiring the dark matter hypothesis.
A Radial Velocity Survey Of Embedded Sources In The Rho Ophiuchi Cluster, Timothy Sullivan, Bruce Wilking, Thomas Greene, Lindsey Lisalda, Erika Gibb, Chemeda Ejeta
A Radial Velocity Survey Of Embedded Sources In The Rho Ophiuchi Cluster, Timothy Sullivan, Bruce Wilking, Thomas Greene, Lindsey Lisalda, Erika Gibb, Chemeda Ejeta
Physics Faculty Works
No abstract provided.
Task-Layer Multiplicity As A Measure Of Community Level Health, Phil Fraundorf
Task-Layer Multiplicity As A Measure Of Community Level Health, Phil Fraundorf
Physics Faculty Works
Te insights of many disciplines, and of commonsense, about individual-level well-being might be strengthened by a shif in focus to community-level well-being in a way that respects belief systems as well as the power of each individual. We start with the jargon of complex systems and the possibility that a small number of broken symmetries, marked by the edges of a hierarchical series of physical subsystem types, underlie the delicate correlation-based complexity of life on our planet’s surface. We show that an information-theory-inspired model of attention-focus on correlation layers, which looks in/out from the boundaries of skin, family, and culture, …
Hypervolatiles In A Jupiter-Family Comet: Observations Of 45p/Honda–Mrkos–Pajdušáková Using Ishell At The Nasa-Irtf, Michael Disanti, Boncho Bonev, Neil Russo, Ronald Vervack, Erika Gibb, Nathan Roth, Adam Mckay, Hideyo Kawakita, Lori Feaga, Harold Weaver
Hypervolatiles In A Jupiter-Family Comet: Observations Of 45p/Honda–Mrkos–Pajdušáková Using Ishell At The Nasa-Irtf, Michael Disanti, Boncho Bonev, Neil Russo, Ronald Vervack, Erika Gibb, Nathan Roth, Adam Mckay, Hideyo Kawakita, Lori Feaga, Harold Weaver
Physics Faculty Works
We used the new high spectral resolution cross-dispersed facility spectrograph, iSHELL, at the NASA Infrared Telescope Facility on Maunakea, HI, to observe Jupiter-family comet (JFC) 45P/Honda–Mrkos–Pajdušáková. We report water production rates, as well as production rates and abundance ratios relative to H2O, for eight trace parent molecules (native ices), CO, CH4, H2CO, CH3OH, HCN, NH3, C2H2, and C2H6, on 2 days spanning UT 2017 January 6/7 and 7/8, shortly following perihelion. Trace species were measured simultaneously with H2O and/or OH prompt emission, a proxy for H2O production, thereby providing a robust and consistent means of establishing the native ice composition …
Beyond 3 Au From The Sun: The Hypervolatiles Ch4, C2h6, And Co In The Distant Comet C/2006 W3 (Christensen), Boncho Bonev, Geronimo Villanueva, Michael Disanti, Hermann Boehnhardt, Manuela Lippi, Erika Gibb, Lucas Paganini, Michael Mumma
Beyond 3 Au From The Sun: The Hypervolatiles Ch4, C2h6, And Co In The Distant Comet C/2006 W3 (Christensen), Boncho Bonev, Geronimo Villanueva, Michael Disanti, Hermann Boehnhardt, Manuela Lippi, Erika Gibb, Lucas Paganini, Michael Mumma
Physics Faculty Works
Comet C/2006 W3 (Christensen) remained outside a heliocentric distance (R h) of 3.1 au throughout its apparition, but it presented an exceptional opportunity to directly sense a suite of molecules released from its nucleus. The Cryogenic Infrared Echelle Spectrograph at ESO-VLT detected infrared emissions from the three "hypervolatiles" (CO, CH4, and C2H6) that have the lowest sublimation temperatures among species that are commonly studied in comets by remote sensing. Even at R h = 3.25 au, the production rate of each molecule exceeded those measured for the same species in a number of other comets, although these comets were observed …
Multiple Phase Transitions In An Agent-Based Evolutionary Model With Neutral Fitness, Sonya Bahar, Dawn King, Adam Scott
Multiple Phase Transitions In An Agent-Based Evolutionary Model With Neutral Fitness, Sonya Bahar, Dawn King, Adam Scott
Physics Faculty Works
Null models are crucial for understanding evolutionary processes such as speciation and adaptive radiation. We analyse an agent-based null model, considering a case without selection—neutral evolution—in which organisms are defined only by phenotype. Universal dynamics has previously been demonstrated in a related model on a neutral fitness landscape, showing that this system belongs to the directed percolation (DP) universality class. The traditional null condition of neutral fitness (where fitness is defined as the number of offspring each organism produces) is extended here to include equal probability of death among organisms. We identify two types of phase transition: (i) a non-equilibrium …
The Composition Of Comet C/2012 K1 (Panstarrs) And The Distribution Of Primary Volatile Abundances Among Comets, Nathan Roth, Erika Gibb, Boncho Bonev, Michael Disanti, Michael Mumma, Geronimo Villanueva, Lucas Paganini
The Composition Of Comet C/2012 K1 (Panstarrs) And The Distribution Of Primary Volatile Abundances Among Comets, Nathan Roth, Erika Gibb, Boncho Bonev, Michael Disanti, Michael Mumma, Geronimo Villanueva, Lucas Paganini
Physics Faculty Works
On 2014 May 22 and 24 we characterized the volatile composition of the dynamically new Oort cloud comet C/2012 K1 (PanSTARRS) using the long-slit, high resolution (λ/Δλ ≈ 25,000) near-infrared echelle spectrograph (NIRSPEC) at the 10 m Keck II telescope on Maunakea, Hawaii. We detected fluorescent emission from six primary volatiles (H2O, HCN, CH4, C2H6, CH3OH, and CO). Upper limits were derived for C2H2, NH3, and H2CO. We report rotational temperatures, production rates, and mixing ratios (relative to water). Compared with median abundance ratios for primary volatiles in other sampled Oort cloud comets, trace gas abundance ratios in C/2012 K1 …
Beyond The Point Charge: Equipotential Surfaces And Electric Fields Of Various Charge Configurations, Jeffrey A. Phillips, Jeff Sanny, David Berube, Anatol Hoemke
Beyond The Point Charge: Equipotential Surfaces And Electric Fields Of Various Charge Configurations, Jeffrey A. Phillips, Jeff Sanny, David Berube, Anatol Hoemke
Physics Faculty Works
A laboratory experiment often performed in an introductory electricity and magnetism course involves the mapping of equipotential lines on a conductive sheet between two objects at different potentials. In this article, we describe how we have expanded this experiment so that it can be used to illustrate the electrostatic properties of conductors. Different configurations of electrodes can be used to show that the electric field is zero inside a conductor as well as within a cavity, the electric field is perpendicular to conducting surfaces, and the charge distribution on conducting surfaces can vary.
Applications Of Fractional Calculus To Newtonian Mechanics, Gabriele U. Varieschi
Applications Of Fractional Calculus To Newtonian Mechanics, Gabriele U. Varieschi
Physics Faculty Works
We investigate some basic applications of Fractional Calculus (FC) to Newtonian mechanics. After a brief review of FC, we consider a possible generalization of Newton's second law of motion and apply it to the case of a body subject to a constant force. In our second application of FC to Newtonian gravity, we consider a generalized fractional gravitational potential and derive the related circular orbital velocities. This analysis might be used as a tool to model galactic rotation curves, in view of the dark matter problem. Both applications have a pedagogical value in connecting fractional calculus to standard mechanics and …
First-Principles Calculated Decomposition Pathways For Libh4 Nanoclusters, Zhi-Quan Huang, Wei-Chih Chen, Feng-Chuan Chuang, Eric Majzoub, Vidvuds Ozoliņš
First-Principles Calculated Decomposition Pathways For Libh4 Nanoclusters, Zhi-Quan Huang, Wei-Chih Chen, Feng-Chuan Chuang, Eric Majzoub, Vidvuds Ozoliņš
Physics Faculty Works
We analyze thermodynamic stability and decomposition pathways of LiBH4 nanoclusters using grand-canonical free-energy minimization based on total energies and vibrational frequencies obtained from density-functional theory (DFT) calculations. We consider (LiBH4)n nanoclusters with n = 2 to 12 as reactants, while the possible products include (Li)n, (B)n, (LiB)n, (LiH)n, and Li2BnHn; off-stoichiometric LinBnHm (m ≤ 4n) clusters were considered for n = 2, 3, and 6. Cluster ground-state configurations have been predicted using prototype electrostatic ground-state (PEGS) and genetic algorithm (GA) based structural optimizations. Free-energy calculations show hydrogen release pathways markedly differ from those in bulk LiBH4. While experiments have found …
Wormhole Geometries In Fourth-Order Conformal Weyl Gravity, Gabriele U. Varieschi, Kellie L. Ault
Wormhole Geometries In Fourth-Order Conformal Weyl Gravity, Gabriele U. Varieschi, Kellie L. Ault
Physics Faculty Works
We present an analysis of the classic wormhole geometries based on conformal Weyl gravity, rather than standard general relativity. The main characteristics of the resulting traversable wormholes remain the same as in the seminal study by Morris and Thorne, namely, that effective super-luminal motion is a viable consequence of the metric. Improving on previous work on the subject, we show that for particular choices of the shape and redshift functions the wormhole metric in the context of conformal gravity does not violate the main energy conditions at or near the wormhole throat. Some exotic matter might still be needed at …
Frame-Invariant Proper-Force, Phil Fraundorf
Frame-Invariant Proper-Force, Phil Fraundorf
Physics Faculty Works
Here we try to find “the best joints for carving up” the phenomenon of accelerated-motion so as to obtain (i)the least need for extended-networks of synchronized-clocks as well as (ii) the greatest frame-independence.The acceleration four-vector’s invariant magnitude, and a number of other quantities from the traveler’spoint of view, show promise for broadening student understanding (and perhaps even practical application)of accelerated motion perspectives at both low and high speeds.
En Route To Destruction: The Evolution In Composition Of Ices In Comet D/2012 S1 (Ison) Between 1.2 And 0.34 Au From The Sun As Revealed At Infrared Wavelengths, M. Disanti, B. Bonev, E. Gibb, L. Paganini, G. Villanueva, M. Mumma, J. Keane, G. Blake, N. Russo, K. Meech, R. Vervack, A. Mckay
En Route To Destruction: The Evolution In Composition Of Ices In Comet D/2012 S1 (Ison) Between 1.2 And 0.34 Au From The Sun As Revealed At Infrared Wavelengths, M. Disanti, B. Bonev, E. Gibb, L. Paganini, G. Villanueva, M. Mumma, J. Keane, G. Blake, N. Russo, K. Meech, R. Vervack, A. Mckay
Physics Faculty Works
We report production rates for H2O and eight trace molecules (CO, C2H6, CH4, CH3OH, NH3, H2CO, HCN, C2H2) in the dynamically new, Sun-grazing Comet C/2012 S1 (ISON), using high-resolution spectroscopy at Keck II and the NASA IRTF on 10 pre-perihelion dates encompassing heliocentric distances Rh = 1.21–0.34 AU. Measured water production rates spanned two orders of magnitude, consistent with a long-term heliocentric power law Q(H2O) ${\rm{\propto }}{R}_{{\rm{h}}}^{(-3.1\pm 0.1)}$. Abundance ratios for CO, C2H6, and CH4 with respect to H2O remained constant with Rh and below their corresponding mean values measured among a dominant sample of Oort Cloud comets. CH3OH was …
Black Hole Shadows In Fourth-Order Conformal Weyl Gravity, Gabriele U. Varieschi, Jonas Mureika
Black Hole Shadows In Fourth-Order Conformal Weyl Gravity, Gabriele U. Varieschi, Jonas Mureika
Physics Faculty Works
We calculate the characteristics of the “black hole shadow” for a rotating, neutral black hole in fourth-order conformal Weyl gravity. It is shown that the morphology is not significantly affected by the underlying framework, except for very large masses. Conformal gravity black hole shadows would also significantly differ from their general relativistic counterparts if the values of the main conformal gravity parameters, γ and κ, were increased by several orders of magnitude. Such increased values for γ and κ are currently ruled out by gravitational phenomenology. Therefore, it is unlikely that these differences in black hole shadows will be detected …
Relative Proper Motions In The Rho Ophiuchi Cluster, Bruce Wilking, Frederick Vrba, Timothy Sullivan
Relative Proper Motions In The Rho Ophiuchi Cluster, Bruce Wilking, Frederick Vrba, Timothy Sullivan
Physics Faculty Works
Near-infrared images optimized for astrometry have been obtained for four fields in the high-density L 1688 cloud core over a 12 year period. The targeted regions include deeply embedded young stellar objects (YSOs) and very low luminosity objects too faint and/or heavily veiled for spectroscopy. Relative proper motions in R.A. and decl. were computed for 111 sources and again for a subset of 65 YSOs, resulting in a mean proper motion of (0,0) for each field. Assuming each field has the same mean proper motion, YSOs in the four fields were combined to yield estimates of the velocity dispersions in …
Sub-Planckian Black Holes And The Generalized Uncertainty Principle, Bernard Carr, Jonas R. Mureika, Piero Nicolini
Sub-Planckian Black Holes And The Generalized Uncertainty Principle, Bernard Carr, Jonas R. Mureika, Piero Nicolini
Physics Faculty Works
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 …
An Optical Spectroscopic Survey Of The Serpens Main Cluster: Evidence For Two Populations?, Kristen Erickson, Bruce Wilking, Michael Meyer, Jinyoung Kim, William Sherry, Matthew Freeman
An Optical Spectroscopic Survey Of The Serpens Main Cluster: Evidence For Two Populations?, Kristen Erickson, Bruce Wilking, Michael Meyer, Jinyoung Kim, William Sherry, Matthew Freeman
Physics Faculty Works
We have completed an optical spectroscopic survey of a sample of candidate young stars in the Serpens Main star-forming region selected from deep B, V, and R band images. While infrared, X-ray, and optical surveys of the cloud have identified many young stellar objects (YSOs), these surveys have been biased toward particular stages of pre-main sequence evolution. We have obtained over 700 moderate resolution optical spectra that, when combined with published data, have led to the identification of 63 association members based on the presence of Hα in emission, lithium absorption, X-ray emission, a mid-infrared excess, and/or reflection nebulosity. Twelve …
How Spherical Is A Cube (Gravitationally)?, Jeff Sanny, David M. Smith
How Spherical Is A Cube (Gravitationally)?, Jeff Sanny, David M. Smith
Physics Faculty Works
An important concept that is presented in the discussion of Newton's law of universal gravitation is that the gravitational effect external to a spherically symmetric mass distribution is the same as if all of the mass of the distribution were concentrated at the center.1,2 By integrating over ring elements of a spherical shell, we show that the gravitational force on a point mass outside the shell is the same as that of a particle with the same mass as the shell at its center. This derivation works for objects with spherical symmetry while depending on the fact that the gravitational …
Astrophysical Tests Of Kinematical Conformal Cosmology In Fourth-Order Conformal Weyl Gravity, Gabriele U. Varieschi
Astrophysical Tests Of Kinematical Conformal Cosmology In Fourth-Order Conformal Weyl Gravity, Gabriele U. Varieschi
Physics Faculty Works
In this work we analyze kinematical conformal cosmology (KCC), an alternative cosmological model based on conformal Weyl gravity (CG), and test it against current type Ia supernova (SNIa) luminosity data and other astrophysical observations. Expanding upon previous work on the subject, we revise the analysis of SNIa data, confirming that KCC can explain the evidence for an accelerating expansion of the Universe without using dark energy or other exotic components. We obtain an independent evaluation of the Hubble constant, H0 = 67:53 kms-1 Mpc-1, very close to the current best estimates. The main KCC and CG parameters are …
C/2013 R1 (Lovejoy) At Ir Wavelengths And The Variability Of Co Abundances Among Oort Cloud Comets, L. Paganini, M. Mumma, G. Villanueva, J. Keane, G. Blake, B. Bonev, M. Disanti, E. Gibb, K. Meech
C/2013 R1 (Lovejoy) At Ir Wavelengths And The Variability Of Co Abundances Among Oort Cloud Comets, L. Paganini, M. Mumma, G. Villanueva, J. Keane, G. Blake, B. Bonev, M. Disanti, E. Gibb, K. Meech
Physics Faculty Works
We report production rates, rotational temperatures, and related parameters for gases in C/2013 R1 (Lovejoy) using the Near InfraRed SPECtrometer at the Keck Observatory, on six UT dates spanning heliocentric distances (Rh ) that decreased from 1.35 AU to 1.16 AU (pre-perihelion). We quantified nine gaseous species (H2O, OH*, CO, CH4, HCN, C2H6, CH3OH, NH3, and NH2) and obtained upper limits for two others (C2H2 and H2CO). Compared with organics-normal comets, our results reveal highly enriched CO, (at most) slightly enriched CH3OH, C2H6, and HCN, and CH4 consistent with "normal", yet depleted, NH3, C2H2, and H2CO. Rotational temperatures increased from …
Kerr Metric, Geodesic Motion, And Flyby Anomaly In Fourth-Order Conformal Gravity, Gabriele U. Varieschi
Kerr Metric, Geodesic Motion, And Flyby Anomaly In Fourth-Order Conformal Gravity, Gabriele U. Varieschi
Physics Faculty Works
In this paper we analyze the Kerr geometry in the context of Conformal Gravity, an alternative theory of gravitation, which is a direct extension of General Relativity (GR). Following previous studies in the literature, we introduce an explicit expression of the Kerr metric in Conformal Gravity, which naturally reduces to the standard GR Kerr geometry in the absence of Conformal Gravity effects. As in the standard case, we show that the Hamilton–Jacobi equation governing geodesic motion in a space-time based on this geometry is indeed separable and that a fourth constant of motion—similar to Carter’s constant—can also be introduced in …
The Unexpectedly Bright Comet C/2012 F6 (Lemmon) Unveiled At Near-Infrared Wavelengths, Lucas Paganini, Michael Disanti, Michael Mumma, Geronimo Villanueva, Boncho Bonev, Jacqueline Keane, Erika Gibb, Hermann Boehnhardt, Karen Meech
The Unexpectedly Bright Comet C/2012 F6 (Lemmon) Unveiled At Near-Infrared Wavelengths, Lucas Paganini, Michael Disanti, Michael Mumma, Geronimo Villanueva, Boncho Bonev, Jacqueline Keane, Erika Gibb, Hermann Boehnhardt, Karen Meech
Physics Faculty Works
We acquired near-infrared spectra of the Oort cloud comet C/2012 F6 (Lemmon) at three different heliocentric distances (R h) during the comet's 2013 perihelion passage, providing a comprehensive measure of the outgassing behavior of parent volatiles and cosmogonic indicators. Our observations were performed pre-perihelion at R h = 1.2 AU with CRIRES (on 2013 February 2 and 4), and post-perihelion at R h = 0.75 AU with CSHELL (on March 31 and April 1) and R h = 1.74 AU with NIRSPEC (on June 20). We detected 10 volatile species (H2O, OH* prompt emission, C2H6, CH3OH, H2CO, HCN, CO, CH4, …
Detection Of Ch4 In The Gv Tau N Protoplanetary Disk, David Horne, Erika Gibb
Detection Of Ch4 In The Gv Tau N Protoplanetary Disk, David Horne, Erika Gibb
Physics Faculty Works
T Tauri stars are low mass young stars that may serve as analogs to the early solar system. Observations of organic molecules in the protoplanetary disks surrounding T Tauri stars are important for characterizing the chemical and physical processes that lead to planet formation. Searches for undetected molecules, particularly in the inner, planet forming regions of these disks are important for testing protoplanetary disk chemical models and for understanding the evolution of volatiles through the star and planet formation process. We used NIRSPEC on Keck 2 to perform a high resolution (λ/Δλ ~ 25,000) L-band survey of T Tauri star …
Ice And Dust In The Prestellar Dark Cloud Lynds 183: Preplanetary Matter At The Lowest Temperatures, David Horne, D. Whittet, C Poteet, J. Chiar, L. Paganini, V Bajaj, S. Shenoy, A Adamson
Ice And Dust In The Prestellar Dark Cloud Lynds 183: Preplanetary Matter At The Lowest Temperatures, David Horne, D. Whittet, C Poteet, J. Chiar, L. Paganini, V Bajaj, S. Shenoy, A Adamson
Physics Faculty Works
Dust grains are nucleation centers and catalysts for the growth of icy mantles in quiescent interstellar clouds, the products of which may accumulate into preplanetary matter when new stars and solar systems form within the clouds. In this paper, we present the first spectroscopic detections of silicate dust and the molecular ices H2O, CO, and CO2 in the vicinity of the prestellar core L183 (L134N). An infrared photometric survey of the cloud was used to identify reddened background stars, and we present spectra covering solid-state absorption features in the wavelength range 2-20 μm for nine of them. The mean composition …
Self-Completeness And Spontaneous Dimensional Reduction, Jonas R. Mureika, Piero Nicolini
Self-Completeness And Spontaneous Dimensional Reduction, Jonas R. Mureika, Piero Nicolini
Physics Faculty Works
A viable quantum theory of gravity is one of the biggest challenges physicists are facing. We discuss the confluence of two highly expected features which might be instrumental in the quest of a finite and renormalizable quantum gravity —spontaneous dimensional reduction and self-completeness. The former suggests the spacetime background at the Planck scale may be effectively two-dimensional, while the latter implies a condition of maximal compression of matter by the formation of an event horizon for Planckian scattering. We generalize such a result to an arbitrary number of dimensions, and show that gravity in higher than four dimensions remains self-complete, …
Spectro-Astrometry Of Water In Dr Tauri, Logan Brown, Matthew Troutman, Erika Gibb
Spectro-Astrometry Of Water In Dr Tauri, Logan Brown, Matthew Troutman, Erika Gibb
Physics Faculty Works
We present high-resolution, near-infrared spectro-astrometric (SA) data for the T Tauri star DR Tau using NIRSPEC at the Keck II telescope. Spectro-astrometry obtains sub-seeing spatial information from emission lines originating in a non-point source object, such as a circumstellar disk. We report the first detection of water SA signatures in a protoplanetary disk. Three water features near 3 μm were averaged together to produce the total signal analyzed. Using a disk model, we constrained the position angle of the disk (~140°), the inclination of the disk (~13°), and the emitting region of the emission lines (~0.056-0.38 AU).
Conformal Gravity And The Alcubierre Warp Drive Metric, Gabriele U. Varieschi, Zily Burstein
Conformal Gravity And The Alcubierre Warp Drive Metric, Gabriele U. Varieschi, Zily Burstein
Physics Faculty Works
We present an analysis of the classic Alcubierre metric based on conformal gravity, rather than standard general relativity. The main characteristics of the resulting warp drive remain the same as in the original study by Alcubierre, that is, effective superluminal motion is a viable outcome of the metric. We show that for particular choices of the shaping function, the Alcubierre metric in the context of conformal gravity does not violate the weak energy condition, as was the case of the original solution. In particular, the resulting warp drive does not require the use of exotic matter. Therefore, if conformal gravity …
Self-Completeness And The Generalized Uncertainty Principle, Maximiliano Isi, Jonas Mureika, Piero Nicolini
Self-Completeness And The Generalized Uncertainty Principle, Maximiliano Isi, Jonas Mureika, Piero Nicolini
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The generalized uncertainty principle discloses a self-complete characteristic of gravity, namely the possibility of masking any curvature singularity behind an event horizon as a result of matter compression at the Planck scale. In this paper we extend the above reasoning in order to overcome some current limitations to the framework, including the absence of a consistent metric describing such Planck-scale black holes. We implement a minimum-size black hole in terms of the extremal configuration of a neutral non-rotating metric, which we derived by mimicking the effects of the generalized uncertainty principle via a short scale modified version of Einstein gravity. …
Primordial Black Hole Evaporation And Spontaneous Dimensional Reduction, Jonas R. Mureika
Primordial Black Hole Evaporation And Spontaneous Dimensional Reduction, Jonas R. Mureika
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Several different approaches to quantum gravity suggest the effective dimension of spacetime reduces from four to two near the Planck scale. In light of such evidence, this Letter re-examines the thermodynamics of primordial black holes (PBHs) in specific lower-dimensional gravitational models. Unlike in four dimensions, (1 + 1)-D black holes radiate with power P ∼ M2BH, while it is known no (2+1)-D (BTZ) black holes can exist in a non-anti-de Sitter universe. This has important relevance to the PBH population size and distribution, and consequently on cosmological evolution scenarios. The number of PBHs that have evaporated to …