Physical Sciences and Mathematics Commons^™

Ds2 As Excitation Of Ads2, Florian Ecker, Daniel Grumiller, Robert Mcnees

Physics: Faculty Publications and Other Works

Title- dS₂ as excitation of AdS₂

We introduce a family of 2D dilaton gravity models with state-dependent constant curvature so that dS₂ emerges as an excitation of AdS₂. Curiously, the strong coupling region corresponds to the asymptotic region geometrically. Apart from these key differences, many features resemble the Almheiri–Polchinski model. We discuss perturbative and non-perturbative thermodynamical stability, bubble nucleation through matter shockwaves, and semiclassical backreaction effects. In some of these models, we find that low temperatures are dominated by AdS₂ but high temperatures are dominated by dS₂, concurrent with a recent proposal …

Characteristics Of Mesospheric Temperature And Gravity Waves Over Chile In 2020-2021, Damien M. Devitt, Kenneth Zia

Physics Capstone Projects

Gravity waves (GWs) are often confused with gravitational waves in the fabric of space time. However, there is a clear distinction between them. Gravity wave is a term used by the atmospheric research field to describe perturbations in the atmosphere. Gravity pulls the perturbations down and causes oscillations, these present in the form of waves. The best visualization is to think of ripples on a pond, as the ripple reaches its peak gravity pulls the ripple down and creates an oscillating effect.

Perturbative Unitarity And Nec Violation In Genesis Cosmology, Yong Cai, Ji Xu, Shuai Zhao, Siyi Zhou

Physics Faculty Publications

Explorations of the violation of null energy condition (NEC) in cosmology could enrich our understanding of the very early universe and the related gravity theories. Although a fully stable NEC violation can be realized in the “beyond Horndeski” theory, it remains an open question whether a violation of the NEC is allowed by some fundamental properties of UV-complete theories or the consistency requirements of effective field theory (EFT). We investigate the tree-level perturbative unitarity for stable NEC violations in the contexts of both Galileon and “beyond Horndeski” genesis cosmology, in which the universe is asymptotically Minkowskian in the past. We …

Roller Coaster Acceleration, Olivia Briggs

Honors Program Theses and Projects

In classical mechanics, Newton’s Second Law (NSL) is often used when talking about acceleration. NSL states that the acceleration of an object is directly related to the net force and inversely related to its mass. It can be written as F~ = m~a. This concept can be applied to many real life situations, one of them being roller coasters. Passengers on roller coasters can accelerate in all directions. Some accelerations are due to gravity while others are due to launch systems that apply a mechanical force to a train. Roller coasters are often described by how many G forces riders …

Dynamics And Stability Of The Two Body Problem With Yukawa Correction, Eli Cavan, Ioannis Haranas, Ioannis Gkigkitzis

Physics and Computer Science Faculty Publications

We explore the dynamics and stability of the two body problem by modifying the Newtonian potential with the Yukawa potential. This model may be considered a theory of modified gravity; where the interaction is not simply the kepler solution for large distance. The stability is investigated by deriving the Jacobian of the linearized matrix equation and evaluating the eigenvalues of the various equilibrium points calculated during the analysis. The subcases of a purely Yukawa and purely Newtonian potential are also explored.

Yang-Mills Sources For Biconformal Gravity, Walter Davis Muhwezi

Physics Capstone Projects

We present a gauge formulation of Yang-Mills matter sources for Biconformal gravity. Biconformal gravity is a 2n-dimensional conformal gauge theory with a curvature linear action that has been shown to reproduce scale invariant general relativity on the cotangent bundle of n-dimensional space time. We present a generalization of Yang-Mills theories in biconformal space and show that the field equations with sources reduce the Yang-Mills sector to n-dimensional Yang-Mills theory in curved spacetime. We compute the restrictive conditions on the energy-momentum tensor required by the gravitational field equations.

Question 1: Clock Variation; Question 2: Recycling Coffee Pods, Larry Weinstein

Physics Faculty Publications

The article presents questions and answers regarding the impact of gravity on pendulum clocks and the recycling of coffee pods.

General Relativity, 3, David Peak

General Relativity

Gravity as geometry: part II

Even in a region of space-time that is so small that tidal effects cannot be detected, gravity still seems to produce curvature. The argument for this point of view starts with the recognition that, for mechanical systems, it is impossible to distinguish a frame of reference with a uniform gravitational field from a uniformly accelerating frame that has no gravity. Thus, for example, in a (small) rocket ship with no windows it is not possible to determine whether the weight one reads standing on a scale at the tail of the rocket is due to …

Unification Of Gravity And Quantum Theory, Adam Daniels

Faculty-Sponsored Student Research & Capstones

An overview of the four fundamental forces of physics as described by the Standard Model (SM) and prevalent unifying theories beyond it is provided. Background knowledge of the particles governing the fundamental forces is provided, as it will be useful in understanding the way in which the unification efforts of particle physics has evolved, either from the SM, or apart from it. It is shown that efforts to provide a quantum theory of gravity have allowed supersymmetry (SUSY) and M-Theory to become two of the prevailing theories for unifying gravity with the remaining non-gravitational forces.

Gravity Sector Of The Sme, Q. G. Bailey

Publications

In this talk, the gravity sector of the effective field theory description of local Lorentz violation is discussed, including minimal and nonminimal curvature couplings. Also, recent experimental and observational analyses including solar-system ephemeris and short-range gravity tests are reviewed.

Studies In Torsion Free Biconformal Spaces, James Thomas Wheeler

All Physics Faculty Publications

We study whether the solutions for the symmetric part of the connection in homogeneous biconformal space also satisfy the more general field equation of curved biconformal spaces. We show that the six field equations for the torsion and co-torsion are satisfied by vanishing torsion together with the Lorentzian form of the metric when γ+ = 0.

Gauge Transformations Of The Biconformal Connection, James Thomas Wheeler

All Physics Faculty Publications

We study the changes of the biconformal gauge fields under the local rotational and dilatational gauge transformations.

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

Physics Faculty Research

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.

Conformal Gravity Holography In Four Dimensions, Daniel Grumiller, Maria Irakleidou, Iva Lovrekovic,, Robert Mcnees

Physics: Faculty Publications and Other Works

We formulate four-dimensional conformal gravity with (anti–)de Sitter boundary conditions that are weaker than Starobinsky boundary conditions, allowing for an asymptotically subleading Rindler term concurrent with a recent model for gravity at large distances. We prove the consistency of the variational principle and derive the holographic response functions. One of them is the conformal gravity version of the Brown–York stress tensor, the other is a “partially massless response”. The on shell action and response functions are finite and do not require holographic renormalization. Finally, we discuss phenomenologically interesting examples, including the most general spherically symmetric solutions and rotating black hole …

Limits On Large Extra Dimensions Based On Observations Of Neutron Stars With The Fermi-Lat, Jay Norris

Physics Faculty Publications and Presentations

We present limits for the compactification scale in the theory of Large Extra Dimensions (LED) proposed by Arkani-Hamed, Dimopoulos, and Dvali. We use 11 months of data from the Fermi Large Area Telescope (Fermi-LAT) to set gamma ray flux limits for 6 gamma-ray faint neutron stars (NS). To set limits on LED we use the model of Hannestad and Raffelt (HR) that calculates the Kaluza-Klein (KK) graviton production in supernova cores and the large fraction subsequently gravitationally bound around the resulting NS. The predicted decay of the bound KK gravitons to γγ should contribute to the flux from NSs. Considering …

Metric Theory Of Gravity With Torsion In An Extra Dimension, Karthik H. Shankar, Anand Balaraman, Kameshwar C. Wali

Department of Physics and Astronomy Faculty Publications

We consider a theory of gravity with a hidden extra dimension and metric-dependent torsion. A set of physically motivated constraints are imposed on the geometry so that the torsion stays confined to the extra dimension and the extra dimension stays hidden at the level of four-dimensional geodesic motion. At the kinematic level, the theory maps onto general relativity, but the dynamical field equations that follow from the action principle deviate markedly from the standard Einstein equations. We study static spherically symmetric vacuum solutions and homogeneous-isotropic cosmological solutions that emerge from the field equations. In both cases, we find solutions of …

The Design And Construction Of A Microgravity Boiling Experiment, Troy Munro

Presentations

No abstract provided.

A Dyad Theory Of Hydrodynamics And Electrodynamics, Preston Jones

Publications

The dyadic calculus is developed in a form suitable for the description of physical relations in curved space. The 4-space equations of hydrodynamics and electrodynamics are constructed using this dyadic calculus. As a demonstration of the relationship between gravity and electrodynamics a time varying metric is shown to generate electromagnetic radiation.

Yang-Mills Gravity In Biconformal Space, L. B. Anderson, James Thomas Wheeler

All Physics Faculty Publications

We write a gravity theory with Yang–Mills-type action using the biconformal gauging of the conformal group. We show that the resulting biconformal Yang–Mills gravity theories describe 4-dim, scale-invariant general relativity in the case of slowly changing fields. In addition, we systematically extend arbitrary 4-dim Yang–Mills theories to biconformal space, providing a new arena for studying flat-space Yang–Mills theories. By applying the biconformal extension to a 4-dim pure Yang–Mills theory with conformal symmetry, we establish a 1-1, onto mapping between a set of gravitational gauge theories and 4-dim, flat-space gauge theories.

Relic Gravitons On Kasner-Like Branes, Marco Cavaglia, G. De Risi, M. Gasperini

Physics Faculty Research & Creative Works

We discuss the cosmological amplification of tensor perturbations in a simple example of brane-world scenario, in which massless gravitons are localized on a higher-dimensional Kasner-like brane embedded in a bulk AdS background. Particular attention is paid to the canonical normalization of the quadratic action describing the massless and massive vacuum quantum fluctuations, and to the exact mass-dependence of the amplitude of massive fluctuations on the brane. The perturbation equations can be separated. In contrast to de Sitter models of brane inflation, we find no mass gap in the spectrum and no enhancement for massless modes at high curvature. The massive …

Approximately Self-Similar Critical Collapse In 2+1 Dimensions, Marco Cavaglia, Gerard Clement, Alessandro Fabbri

Physics Faculty Research & Creative Works

Critical collapse of a self-gravitating scalar field in a (2+1)-dimensional spacetime with negative cosmological constant seems to be dominated by a continuously self-similar solution of the field equations without cosmological constant. However, previous studies of linear perturbations in this background were inconclusive. We extend the continuously self-similar solutions to solutions of the field equations with negative cosmological constant, and analyze their linear perturbations. The extended solutions are characterized by a continuous parameter. A suitable choice of this parameter seems to improve the agreement with the numerical results. We also study the dynamics of the apparent horizon in the extended background.

Black Hole Multiplicity At Particle Colliders (Do Black Holes Radiate Mainly On The Brane?), Marco Cavaglia

Physics Faculty Research & Creative Works

If gravity becomes strong at the TeV scale, we may have the chance to produce black holes at particle colliders. In this Letter we revisit some phenomenological signatures of black hole production in TeV-gravity theories. We show that the bulk-to-brane ratio of black hole energy loss during the Hawking evaporation phase depends crucially on the black hole greybody factors and on the particle degrees of freedom. Since the greybody factors have not yet been calculated in the literature, and the particle content at trans-Planckian energies is not known, it is premature to claim that the black hole emits mainly on …

Tev Black Hole Fragmentation And Detectability In Extensive Air Showers, Eun-Joo Ahn, Maximo Ave, Marco Cavaglia, Angela V. Olinto

Physics Faculty Research & Creative Works

In models with large extra dimensions, particle collisions with a center-of-mass energy larger than the fundamental gravitational scale can generate nonperturbative gravitational objects. Since cosmic rays have been observed with energies above 10⁸ TeV, gravitational effects in the TeV energy range can, in principle, be observed by ultrahigh energy cosmic ray detectors. We consider the interaction of ultrahigh energy neutrinos in the atmosphere and compare extensive air showers from TeV black hole formation and fragmentation with standard model processes. Departures from the standard model predictions arise in the interaction cross sections and in the multiplicity of secondary particles. Large …

Brane Factories, Eun-Joo Ahn, Marco Cavaglia, Angela V. Olinto

Physics Faculty Research & Creative Works

We propose that higher-dimensional extended objects (p-branes) are created by super-Planckian scattering processes in theories with TeV scale gravity. As an example, we compute the cross section for p-brane creation in a (n + 4)-dimensional spacetime with asymmetric compactification. We find that the cross section for the formation of a brane which is wounded on a compact submanifold of size of the fundamental gravitational scale is larger than the cross section for the creation of a spherically symmetric black hole. Therefore, we predict that branes are more likely to be created than black holes in super-Planckian …

Two-Dimensional Ds/Cft Correspondence, Mariano Cadoni, P. Carta, Marco Cavaglia, S. Mignemi

Physics Faculty Research & Creative Works

We investigate de Sitter/conformal field theory (dS/CFT) correspondence in two dimensions. We define the conserved mass of de Sitter spacetime and formulate the correspondence along the lines of the anti–de Sitter/conformal field theory duality. The asymptotic symmetry group, mass, and central charge of de Sitter spacetime are equal to those of anti–de Sitter spacetime. The entropy of two-dimensional de Sitter spacetime is evaluated by applying the Cardy formula. We calculate the boundary correlators induced by the propagation of the dilaton in two-dimensional de Sitter space. Although the dilaton is a tachyonic perturbation in the bulk, boundary conformal correlators have a …

Open Strings, 2d Gravity, And Ads/Cft Correspondence, Mariano Cadoni, Marco Cavaglia

Physics Faculty Research & Creative Works

We present a detailed discussion of the duality between dilaton gravity on AdS₂ and open strings. The correspondence between the two theories is established using their symmetries and field theoretical, thermodynamic, and statistical arguments. We use the dual conformai field theory to describe two-dimensional black holes. In particular, all the semiclassical features of the black holes, including the entropy, have a natural interpretation in terms of the dual microscopic conformai dynamics. The previous results are discussed in the general framework of the anti-de Sitter/conformal field theory dualities.

Gravity And Electromagnetism In Noncommutative Geometry, Giovanni Landi, Nguyen Ai Viet, Kameshwar C. Wali

Physics - All Scholarship

We present a unified description of gravity and electromagnetism in the framework of a Z 2 non-commutative differential calculus. It can be considered as a “discrete version” of Kaluza-Klein theory, where the fifth continuous dimension is replaced by two discrete points. We derive an action which coincides with the dimensionally reduced one of the ordinary Kaluza-Klein theory.

String Induced Space Compactification, P. G. Freund, P. Oh, James Thomas Wheeler

All Physics Faculty Publications

Motivated by the possibility of a finite theory of gravity provided by superstrings in ten space-time dimensions, we analyze the problem of space compactification in the context of string dynamics. Such an analysis is hampered by conceptual and technical problems, stemming from the existence of the quantum string's own graviton mode on the one hand, and from Witten's observation of anomalies in a not specially chosen curves space-time on the other hand. Still, in the context of a classical local field presentation of string theory à la Nambu and Hosotani, supplemented by gravitational and Kalb-Ramond interactions, we are able to …