Open Access. Powered by Scholars. Published by Universities.®
- Discipline
-
- Astrophysics and Astronomy (37)
- Cosmology, Relativity, and Gravity (21)
- Other Physics (12)
- Elementary Particles and Fields and String Theory (10)
- Quantum Physics (7)
-
- Arts and Humanities (3)
- Mathematics (3)
- Other Astrophysics and Astronomy (3)
- Philosophy (3)
- Philosophy of Science (3)
- External Galaxies (2)
- Algebra (1)
- Applied Mathematics (1)
- Computer Sciences (1)
- Engineering (1)
- Engineering Physics (1)
- Engineering Science and Materials (1)
- Geometry and Topology (1)
- Instrumentation (1)
- Mechanical Engineering (1)
- Mechanics of Materials (1)
- Metaphysics (1)
- Nuclear (1)
- Numerical Analysis and Scientific Computing (1)
- Optics (1)
- Physical Processes (1)
- Religion (1)
- Statistical, Nonlinear, and Soft Matter Physics (1)
- Institution
-
- University of Kentucky (10)
- Dartmouth College (7)
- Prairie View A&M University (7)
- TÜBİTAK (7)
- Old Dominion University (5)
-
- The University of San Francisco (5)
- University of New Mexico (5)
- University of Texas Rio Grande Valley (4)
- Boise State University (3)
- Syracuse University (3)
- Utah State University (3)
- Chapman University (2)
- DePaul University (2)
- Liberty University (2)
- Loyola Marymount University and Loyola Law School (2)
- Swarthmore College (2)
- University of Mary Washington (2)
- Bridgewater State University (1)
- California Polytechnic State University, San Luis Obispo (1)
- City University of New York (CUNY) (1)
- Michigan Technological University (1)
- Missouri University of Science and Technology (1)
- Northern Illinois University (1)
- Southern Methodist University (1)
- University at Albany, State University of New York (1)
- University of Mississippi (1)
- University of South Carolina (1)
- University of South Florida (1)
- Virginia Commonwealth University (1)
- Western Kentucky University (1)
- Publication Year
- Publication
-
- Physics and Astronomy Faculty Publications (10)
- Applications and Applied Mathematics: An International Journal (AAM) (7)
- Turkish Journal of Physics (7)
- Dartmouth Scholarship (5)
- Physics Faculty Publications (5)
-
- Physics and Astronomy (5)
- Physics & Astronomy Faculty Publications (4)
- Physics & Astronomy ETDs (3)
- Physics Faculty Publications and Presentations (3)
- Branch Mathematics and Statistics Faculty and Staff Publications (2)
- Dartmouth College Ph.D Dissertations (2)
- Departmental Honors & Graduate Capstone Projects (2)
- Mathematics, Physics, and Computer Science Faculty Articles and Research (2)
- Physics & Astronomy Faculty Works (2)
- Physics - Dissertations (2)
- Physics Faculty Works (2)
- Theses and Dissertations (2)
- All Graduate Theses and Dissertations, Fall 2023 to Present (1)
- All Physics Faculty Publications (1)
- College of Science and Health Theses and Dissertations (1)
- DePaul Discoveries (1)
- Dissertations - ALL (1)
- Dissertations, Theses, and Capstone Projects (1)
- Electronic Theses and Dissertations (1)
- Faculty Publications and Presentations (1)
- Graduate Research Theses & Dissertations (1)
- Honors Program Theses and Projects (1)
- Legacy Theses & Dissertations (2009 - 2024) (1)
- Mahurin Honors College Capstone Experience/Thesis Projects (1)
- Masters Theses (1)
- Publication Type
Articles 61 - 85 of 85
Full-Text Articles in Physics
Cosmic Sound In The Lyman Alpha Forest, Spencer Everett, Matt Kwiecien, Cordell Newmiller
Cosmic Sound In The Lyman Alpha Forest, Spencer Everett, Matt Kwiecien, Cordell Newmiller
DePaul Discoveries
Using the Baryon Oscillation Spectroscopic Survey (BOSS) from the Sloan Digital Sky Survey (SDSS), the authors attempt to detect the baryonic acoustic oscillations (BAOs) using the discrete wavelet transform. The wavelet transform is used to construct the power spectrum of intergalactic clouds of matter at large (Mpc) distance scales. It was found that the wavelet transform used here does not have high enough resolution to detect the BAOs. However, the techniques used in this study allow for future improvements in the transform that could potentially resolve the expected peak in the power spectrum and indicate the existence of BAOs.
String Fluid Cosmological Model With Magnetic Field In Bimetric Theory Of Gravitation, M. S. Borkar, N. P. Gaikwad
String Fluid Cosmological Model With Magnetic Field In Bimetric Theory Of Gravitation, M. S. Borkar, N. P. Gaikwad
Applications and Applied Mathematics: An International Journal (AAM)
In this paper, LRS Bianchi type I string fluid cosmological model with magnetic field in bimetric theory of gravitation is investigated by assuming barotropic equation of state for pressure and density and assuming the bulk viscosity to be inversely proportional to the scalar expansion. The source of energy momentum tensor is a bulk viscous fluid containing one dimensional string with electromagnetic field. The physical and geometrical properties of the model are discussed. The bulk viscosity affected the whole properties of the model.
Lensed Type Ia Supernovae As Probes Of Cluster Mass Models, J Nordin, David Rubin, J Richard, E Rykoff, Greg Aldering, R Amanullah, H Atek, K Barbary, S Deustua, H K. Fakhouri, A S. Fruchter, A Goobar, I Hook, E Y. Hsiao, Xiaosheng Huang, J P. Kneib, C Lidman, J Meyers, S Perlmutter, C Saunders, A L. Spadafora, N Suzuki
Lensed Type Ia Supernovae As Probes Of Cluster Mass Models, J Nordin, David Rubin, J Richard, E Rykoff, Greg Aldering, R Amanullah, H Atek, K Barbary, S Deustua, H K. Fakhouri, A S. Fruchter, A Goobar, I Hook, E Y. Hsiao, Xiaosheng Huang, J P. Kneib, C Lidman, J Meyers, S Perlmutter, C Saunders, A L. Spadafora, N Suzuki
Physics and Astronomy
Using three magnified Type Ia supernovae (SNe Ia) detected behind CLASH (Cluster Lensing and Supernovae with Hubble) clusters, we perform a first pilot study to see whether standardizable candles can be used to calibrate cluster mass maps created from strong lensing observations. Such calibrations will be crucial when next-generation Hubble Space Telescope cluster surveys (e.g. Frontier) provide magnification maps that will, in turn, form the basis for the exploration of the high-redshift Universe. We classify SNe using combined photometric and spectroscopic observations, finding two of the three to be clearly of Type Ia and the third probable. The SNe exhibit …
It's About Time: Dynamics Of Inflationary Cosmology As The Source Of The Asymmetry Of Time, Emre Keskin
It's About Time: Dynamics Of Inflationary Cosmology As The Source Of The Asymmetry Of Time, Emre Keskin
USF Tampa Graduate Theses and Dissertations
This project is about the asymmetry of time. The main source of discontent for physicists and philosophers alike is that even though in every physical theory we developed and/or discovered for explaining how the universe functions, the laws are time reversal invariant; there seems to be a very genuine asymmetry between the past and the future. The aim of this project is to examine several attempts to solve this friction between the laws of physics and the asymmetry and provide a new proposal that makes use of modern cosmology. In the recent history of physics and in contemporary philosophy of …
Constraints On Cosmic Strings From The Ligo-Virgo Gravitational-Wave Detectors, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
Constraints On Cosmic Strings From The Ligo-Virgo Gravitational-Wave Detectors, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
Physics Faculty Research & Creative Works
Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs …
Cosmological And Astrophysical Tests Of Modified Gravity, Caixia Gao
Cosmological And Astrophysical Tests Of Modified Gravity, Caixia Gao
Electronic Theses and Dissertations
Three alternative theories to general relativity will be studied. The aim is to test these theories by applying them to astronomical objects or the cosmological background. The first one is unimodular relativity. The cosmological perturbation theory of this model is studied and the predictions on temperature fluctuations of the cmb are found. The second one is drgt massive gravity. In this theory a charged black hole solution is found and compared to those in gr, folloby constraints on the parameter space. The third one is a general massive gravity theory which shares the same background equation with the massless case …
Bianchi Type I Magnetized Cosmological Model With Λ-Term In Bimetric Theory Of Gravitation, M. S. Borkar, S. S. Charjan
Bianchi Type I Magnetized Cosmological Model With Λ-Term In Bimetric Theory Of Gravitation, M. S. Borkar, S. S. Charjan
Applications and Applied Mathematics: An International Journal (AAM)
In this paper, we investigated Bianchi Type I magnetized cosmological model with cosmological constant in Rosen’s bimetric theory of gravitation by using the techniques of Letelier and Stachel. The nature of the model is discussed in presence as well as in absence of the magnetic field and cosmological constant. Our model exists and it never goes to vacuum if cosmological constant is not equal to zero and for finite value of cosmic time. In the presence of magnetic field, our model goes to vacuum when the cosmic time tends to minus infinity. Further in the absence of magnetic field the …
The Fine-Tuning Of Nomic Behavior In Multiverse Scenarios, Max Lewis Edward Andrews
The Fine-Tuning Of Nomic Behavior In Multiverse Scenarios, Max Lewis Edward Andrews
Masters Theses
The multiverse hypothesis (the view that there is not just one world or universe in existence, bur rather that there are many) is the leading alternative to the competing fine-tuning hypothesis (the laws of physics and constants are fine-tuned for the existence of life). The multiverse dispels many aspects of the fine-tuning argument by suggesting that there are different initial conditions in each universe, varying constants of physics, and the laws of nature lose their known arbitrary values; thus, making the previous single-universe argument from fine- tuning incredibly weak. The position that will be advocated will be that a form …
Primordial Black Hole Evaporation And Spontaneous Dimensional Reduction, Jonas R. Mureika
Primordial Black Hole Evaporation And Spontaneous Dimensional Reduction, Jonas R. Mureika
Physics Faculty Works
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 …
Effective Field Theories In Cosmology, Riccardo Penco
Effective Field Theories In Cosmology, Riccardo Penco
Physics - Dissertations
During the last 20 years, a large amount of detailed cosmological observations have promoted cosmology to the rank of high-precision science. Remarkably, all the observations currently available can be accounted for by assuming that (i) the universe is approximately homogeneous and isotropic on large scales, (ii) gravitational interactions are described by General Relativity with a non-vanishing cosmological constant and (ii) 85% of the matter content of the universe is in the form of dark matter, a presently unknown type of matter which interacts with ordinary matter only gravitationally. Current theoretical efforts are focused on …
Bianchi-V Cosmological Models With Viscous Fluid And Constant Deceleration Parameter In General Relativity, Sharad Kandalkar, Pramod Khade, Mohini Gaikwad
Bianchi-V Cosmological Models With Viscous Fluid And Constant Deceleration Parameter In General Relativity, Sharad Kandalkar, Pramod Khade, Mohini Gaikwad
Turkish Journal of Physics
In this paper we discuss the variation law for Hubble's parameter, average scale factor in spatially homogenous anisotropic Bianchi Type V space-time that yields a constant value deceleration parameter. Using the law of variation for Hubble's parameter, exact solutions of Einstein's field equations are obtained for Bianchi-V space time filled with viscous fluid in two different cases where the universe exhibits power law and exponential expansion. We investigate a number of solutions with constant and time varying cosmological constant together with variable and constant bulk viscosity. We find that the constant value of deceleration parameter is reasonable for the present …
Everything Is Entangled, Roman V. Buniy, Stephen D. H. Hsu
Everything Is Entangled, Roman V. Buniy, Stephen D. H. Hsu
Mathematics, Physics, and Computer Science Faculty Articles and Research
We show that big bang cosmology implies a high degree of entanglement of particles in the universe. In fact, a typical particle is entangled with many particles far outside our horizon. However, the entanglement is spread nearly uniformly so that two randomly chosen particles are unlikely to be directly entangled with each other - the reduced density matrix describing any pair is likely to be separable.
The Hubble Space Telescope * Cluster Supernova Survey. Ii. The Type Ia Supernova Rate In High-Redshift Galaxy Clusters, K Barbary, G Aldering, R Amanullah, M Brodwin, N Connolly, Ks Dawson, M Doi, P Eisenhardt, L Faccioli, V Fadeyev, Hk Fakhouri, As Fruchter, D G. Gilbank, Md Gladders, G Goldhaber, A Goobar, T Hattori, E Hsiao, Xiaosheng Huang, Y Ihara, K Kashikawa, B Koester, K Konishi, M Kowalski, C Lidman, L Lubin, J Meyers, T Morokuma, T Oda, N Panagia, S Perlmutter, M Postman, P Ripoche, P Rosati, D Rubin, Dj Schlegel, Al Spadafora, Sa Stanford, M Strovink, N Suzuki, N Takanashi, K Tokita, N Yasuda
The Hubble Space Telescope * Cluster Supernova Survey. Ii. The Type Ia Supernova Rate In High-Redshift Galaxy Clusters, K Barbary, G Aldering, R Amanullah, M Brodwin, N Connolly, Ks Dawson, M Doi, P Eisenhardt, L Faccioli, V Fadeyev, Hk Fakhouri, As Fruchter, D G. Gilbank, Md Gladders, G Goldhaber, A Goobar, T Hattori, E Hsiao, Xiaosheng Huang, Y Ihara, K Kashikawa, B Koester, K Konishi, M Kowalski, C Lidman, L Lubin, J Meyers, T Morokuma, T Oda, N Panagia, S Perlmutter, M Postman, P Ripoche, P Rosati, D Rubin, Dj Schlegel, Al Spadafora, Sa Stanford, M Strovink, N Suzuki, N Takanashi, K Tokita, N Yasuda
Physics and Astronomy
We report a measurement of the Type Ia supernova (SN Ia) rate in galaxy clusters at 0.9 < z < 1.46 from the Hubble Space Telescope Cluster Supernova Survey. This is the first cluster SN Ia rate measurement with detected z > 0.9 SNe. Finding 8 ± 1 cluster SNe Ia, we determine an SN Ia rate of 0.50+0.23 –0.19 (stat) +0.10 –0.09 (sys) h 2 70 SNuB (SNuB ≡ 10–12 SNe L –1 ☉, B yr–1). In units of stellar mass, this translates to 0.36+0.16 –0.13 (stat) +0.07 –0.06 (sys) h 2 70 SNuM (SNuM ≡ 10–12 SNe M –1 ☉ yr–1). This represents a …
Predictability Time Of Chaotic Cosmologies, John Max Wilson
Predictability Time Of Chaotic Cosmologies, John Max Wilson
Mahurin Honors College Capstone Experience/Thesis Projects
We examine the predictability time scales for a cosmological model from the Einstein field equations coupled to the Klein-Gordon equations for a spin zero scalar field with an interaction potential V(φ). The cosmological equations resulting from this coupling are nonlinear in the scale cosmic parameter and scalar field, thus exhibiting characteristics of chaos. The equations can be linearized in the neighborhood of equilibrium points and then diagonalized to yield its Lyapunov exponents. One e-folding time of the system is then found to estimate the predictability time. This time is compared to the Big Rip time theorized by Yurov, Moruno, and …
Topics In Cosmic Acceleration And Braneworlds, Eric J. West
Topics In Cosmic Acceleration And Braneworlds, Eric J. West
Physics - Dissertations
Cosmic acceleration has come to be a standard, and perhaps required, ingredient in our current understanding of the universe. In the early universe, under the name of inflation, a phase of accelerated expansion is used to solve many problems with the standard Hot Big Bang cosmology. In the late universe, cosmic acceleration seems to best explain a wide variety of observations. In both cases, we lack a complete theory of what drives cosmic acceleration. In this thesis I discuss some open issues in our understanding of cosmic acceleration, both in the early and late universe.
Prospective Type Ia Supernova Surveys From Dome A, A. Kim, A. Bonissent, Jodi L. Christiansen, A. Ealet, L. Faccioli, L. Gladney, G. Kushner, E. Linder, C. Stoughton, L. Wang
Prospective Type Ia Supernova Surveys From Dome A, A. Kim, A. Bonissent, Jodi L. Christiansen, A. Ealet, L. Faccioli, L. Gladney, G. Kushner, E. Linder, C. Stoughton, L. Wang
Physics
Dome A, the highest plateau in Antarctica, is being developed as a site for an astronomical observatory. The planned telescopes and instrumentation and the unique site characteristics are conducive toward Type Ia supernova surveys for cosmology. A self-contained search and survey over five years can yield a spectro-photometric time series of ∼1000 z < 0.08 supernovae. These can serve to anchor the Hubble diagram and quantify the relationship between luminosities and heterogeneities within the Type Ia supernova class, reducing systematics. Larger aperture (>4-m) telescopes are capable of discovering supernovae shortly after explosion out to z ∼ 3. These can be fed to space telescopes, and can isolate systematics and extend the redshift range over which we measure the expansion history of the universe.
On Robertson-Walker Universe Model With Variable Cosmological Term And Gravitational Constant In Cosmological Relativity Theory, Kangujam Priyokumar Singh
On Robertson-Walker Universe Model With Variable Cosmological Term And Gravitational Constant In Cosmological Relativity Theory, Kangujam Priyokumar Singh
Turkish Journal of Physics
This paper presents cosmological models in which the gravitational and cosmological constants G and \Lambda are time-dependent. We find a variety of solutions for the variation of cosmological parameters. It is also found that, in the case of matter dominated Robertson-Walker Universe, if the cosmological constant \Lambda \ne 0, the Hubble's constant H is not constant at all but inversely proportional to the cosmic time. The conservation law for the energy momentum tensor is still valid with our law of variation: \Lambda \propto R^{-2} and G\rho \propto \frac{\Lambda }{8\pi}.
Kantowski-Sachs Viscous Fluid Cosmological Model With A Varying \Lambda, Sharad Kandalkar, Pramod Khade, Sunita Gawande
Kantowski-Sachs Viscous Fluid Cosmological Model With A Varying \Lambda, Sharad Kandalkar, Pramod Khade, Sunita Gawande
Turkish Journal of Physics
We study the Kantowski-Sachs cosmological model filled with viscous fluid in the presence of cosmological term \Lambda. To get a deterministic solution, a condition between metric potentials is used. The viscous coefficient of bulk viscous fluid is assumed to be a power function of mass density, whereas coefficient of shear viscosity is considered proportional to scale of expansion in the model. It is found that the cosmological constant \Lambda is positive and is a decreasing function of time, which is supported by results from recent supernova observations. Some physical and geometrical properties of the models are also discussed.
Energy Landscape Of D -Dimensional Q -Balls, Marcelo Gleiser, Joel Thorarinson
Energy Landscape Of D -Dimensional Q -Balls, Marcelo Gleiser, Joel Thorarinson
Dartmouth Scholarship
We investigate the properties of Q-balls in d spatial dimensions. First, a generalized virial relation for these objects is obtained. We then focus on potentials V(ϕϕ†)=∑3n=1an(ϕϕ†)n, where an is a constant and n is an integer, obtaining variational estimates for their energies for arbitrary charge Q. These analytical estimates are contrasted with numerical results and their accuracy evaluated. Based on the results, we offer a simple criterion to classify large and small d-dimensional Q-balls for this class of potentials. A minimum charge is then computed and its dependence on spatial dimensionality is shown to scale as Qmin∼exp(d). We also briefly …
Cosmic Shear Of The Microwave Background: The Curl Diagnostic, Asantha Cooray, Marc Kamionkowski, Robert R. Caldwell
Cosmic Shear Of The Microwave Background: The Curl Diagnostic, Asantha Cooray, Marc Kamionkowski, Robert R. Caldwell
Dartmouth Scholarship
Weak-lensing distortions of the cosmic-microwave-background (CMB) temperature and polarization patterns can reveal important clues to the intervening large-scale structure. The effect of lensing is to deflect the primary temperature and polarization signal to slightly different locations on the sky. Deflections due to density fluctuations, gradient-type for the gradient of the projected gravitational potential, give a direct measure of the mass distribution. Curl-type deflections can be induced by, for example, a primordial background of gravitational waves from inflation or by second-order effects related to lensing by density perturbations. Whereas gradient-type deflections are expected to dominate, we show that curl-type deflections can …
Lisa Data Analysis: Doppler Demodulation, Neil J. Cornish, Shane L. Larson
Lisa Data Analysis: Doppler Demodulation, Neil J. Cornish, Shane L. Larson
All Physics Faculty Publications
The orbital motion of the Laser Interferometer Space Antenna (LISA) produces amplitude, phaseand frequency modulation of a gravitational wave signal. The modulations have the effect of spreading a monochromatic gravitational wave signal across a range of frequencies. The modulations encode useful information about the source location and orientation, but they also have the deleteriousaffect of spreading a signal across a wide bandwidth, thereby reducing the strength of the signalrelative to the instrument noise. We describe a simple method for removing the dominant, Doppler,component of the signal modulation. The demodulation reassembles the power from a monochromatic source into a narrow spike, …
A First Principles Warm Inflation Model That Solves The Cosmological Horizon And Flatness Problems, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos
A First Principles Warm Inflation Model That Solves The Cosmological Horizon And Flatness Problems, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos
Dartmouth Scholarship
A quantum field theory warm inflation model is presented that solves the horizon and flatness problems. The model obtains, from the elementary dynamics of particle physics, cosmological scale factor trajectories that begin in a radiation dominated regime, enter an inflationary regime, and then smoothly exit back into a radiation dominated regime, with non-negligible radiation throughout the evolution.
Strong Dissipative Behavior In Quantum Field Theory, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos
Strong Dissipative Behavior In Quantum Field Theory, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos
Dartmouth Scholarship
We study the conditions under which an overdamped regime can be attained in the dynamic evolution of a quantum field configuration. Using a real-time formulation of finite temperature field theory, we compute the effective evolution equation of a scalar field configuration, quadratically interacting with a given set of other scalar fields. We then show that, in the overdamped regime, the dissipative kernel in the field equation of motion is closely related to the shear viscosity coefficient, as computed in scalar field theory at finite temperature. The effective dynamics is equivalent to a time-dependent Ginzburg-Landau description of the approach to equilibrium …
Oscillons: Resonant Configurations During Bubble Collapse, E J. Copeland, M Gleiser, H R. Müller
Oscillons: Resonant Configurations During Bubble Collapse, E J. Copeland, M Gleiser, H R. Müller
Dartmouth Scholarship
Oscillons are localized, non-singular, time-dependent, spherically-symmetric solutions of nonlinear scalar field theories which, although unstable, are extremely long-lived. We show that they naturally appear during the collapse of subcritical bubbles in models with symmetric and asymmetric double-well potentials. By a combination of analytical and numerical work we explain several of their properties, including the conditions for their existence, their longevity, and their final demise. We discuss several contexts in which we expect oscillons to be relevant. In particular, their nucleation during cosmological phase transitions may have wide-rangingconsequences.
The Origin Of N Iii Λ990 And C Iii Λ977 Emission In Agn Narrow-Line Region Gas, Jason W. Ferguson, Gary J. Ferland, A. K. Pradham
The Origin Of N Iii Λ990 And C Iii Λ977 Emission In Agn Narrow-Line Region Gas, Jason W. Ferguson, Gary J. Ferland, A. K. Pradham
Physics and Astronomy Faculty Publications
We discuss implications of Hopkins Ultraviolet Telescope (HUT) detections of C III λ977 and N III λ990 emission from the narrow-line region of the Seyfert 2 galaxy NGC 1068. In their discovery paper Kriss et al. showed that the unexpectedly great strength of these lines implies that the emitting gas must be shock-heated if the lines are collisionally excited. Here we investigate other processes which excite these lines in photoionization equilibrium. Recombination, mainly dielectronic, and continuum fluorescence are strong contributors to the line. The resulting intensities are sensitive to the velocity field of the emitting gas and require …