Deontic Modality and the Semantics of Choice

I propose a unified solution to two puzzles: Ross's puzzle and free choice permission. I begin with a pair of cases from the decision theory literature illustrating the phenomenon of act dependence, where what an agent ought to do depends on what she does. The notion of permissibility distilled from these cases forms the basis for my analysis of 'may' and 'ought'. This framework is then combined with a generalization of the classical semantics for disjunction — equivalent to Boolean disjunction on the diagonal, but with a different two-dimensional character — that explains the puzzling facts in terms of semantic consequenc

A Two-Dimensional Logic for Two Paradoxes of Deontic Modality

In this paper, we axiomatize the deontic logic in Fusco 2015, which uses a Stalnaker-inspired account of diagonal acceptance and a two-dimensional account of disjunction to treat Ross’s Paradox and the Puzzle of Free Choice Permission. On this account, disjunction-involving validities are a priori rather than necessary. We show how to axiomatize two-dimensional disjunction so that the introduction/elimination rules for boolean disjunction can be viewed as one-dimensional projections of more general two-dimensional rules. These completeness results help make explicit the restrictions Fusco’s account must place on free-choice inferences. They are also of independent interest, as they raise difficult questions about how to ‘lift’ a Kripke frame for a one- dimensional modal logic into two dimensions

The Grizzly, April 30, 1982

Speakers Announced for Graduation • New Tuition Plan Announced • Letters to the Editor • Aims for 1982-86 Present Concern for Administration • Japanese Exchange Students Visit in August • President\u27s Corner • Women\u27s Club Continues to Support Campus • An Ursinus Friday Night • Students Direct One Act Plays • USGA Notes • Sports Profile: Jeff Grassie • Lacrosse Skids • UC Track and Field Heads to MAC • Tough Luck Bears Lose 4-1 • Women\u27s Tennis Eliminated From MAC • Penn State Dumps Women\u27s Lacrossehttps://digitalcommons.ursinus.edu/grizzlynews/1080/thumbnail.jp

The Grizzly, April 23, 1982

Recurring Thefts Plague New Men\u27s Dorm • Final Forum Discusses Use of Photography in Space • Too Much Grass on Campus? • Letters to the Editor • Congress Puts Hold on Financial Aid Cuts • Reagan\u27s Change of Style • Vanities Well Received by Community • Hooters Reggae Keeps UC Jumping • UC Baseball Splits With Widener • Men\u27s Tennis Top Widener • Bear Blades Finish Season Strong • Women\u27s Tennis Head to MACs • Women\u27s Track Club Earns First Place • Temple Dumps Women\u27s Lacrosse • Men\u27s Lacrosse is on Trackhttps://digitalcommons.ursinus.edu/grizzlynews/1079/thumbnail.jp

The Grizzly, April 2, 1982

PA Special Olympics This Weekend • Room Selection Continues • Student Publications Staffs Chosen • Parents Day Plans Offer Variety of Talents • USGA Notes • Letters to the Editor • Dean of College Accepting Nominations for Lindback Award • Class Elections Next Week • News Briefs: Hooters Concert Tickets Now Available; Friends of Library Book Sale; Senior Women Invited to Parents Day Reception; Photography in Space Topic of Final Forum; Scholarship Offered for Students of Hellenic Descent • Food Day: A Chance to Share the Wealth • New Library Survey Conducted • Alumna Presents DuPont Grant • Students Direct Comedy Series • Duet Takes First in Talent Show • F&M Tops Track Team • W\u27s Tennis Drops Warm-up • Division 1 West Chester a Little Too Strong • MAC Champs Back • Harvard Slips by Lady Bears • Batsmen Split Twin Bill • Softball Team Takes Two Out of Threehttps://digitalcommons.ursinus.edu/grizzlynews/1077/thumbnail.jp

The Grizzly, February 13, 1981

Water Crisis Worsens: TCE Also a Problem • Pett Leaving Economics Department • Mobley Breaks Basketball Record • News Briefs: Meistersingers concert in Oreland; Ursinus professor published • Departmental Focus: English Department; History Department • Orientation Committee Applications Being Taken • 1981 Fraternity Pledge Classes • Music News • Female Artists Topic of Forum • Coffeehouse: A Folk Touch • Candidates for USGA Offices • Women\u27s B-Ball Undefeated 9 Straight • Tight Season Ahead for Intramural B-Ball • Badminton Team Playin\u27 Tough • Hoopsters Claim Two More Victims • Grizzly Grapplers Mark at 7-4-1 • Aquabears Dunk Foes: Swimmers Living Up to .500 Goalhttps://digitalcommons.ursinus.edu/grizzlynews/1052/thumbnail.jp

The Grizzly, October 3, 1980

Administration Focuses Attention On Pledging • Ritter Investigation Continues • Strangers Vandalize Beardwood Extinguishers • USGA Sponsors Alcohol Awareness Program • Women Experience the Excitement of Bid Day • College Disciplines Two Fraternities • Prof Appointed in Ec/BA • Photography Course Offered In Evening School • Values Education Examined By Committee • Candidates\u27 Platforms for Campus Elections • Classes of \u2781, \u2783 to Sponsor Gong Show • Album Review: Panorama: New View New Wave • Time Square Is Sheer Inspiration • Rush Returns to Philadelphia After Long Delay • Dingy Room Ideas Vol. II • Field Hockey Ties W&M; Beats Gettysburg • Volleyball Lookin\u27 Good • Awesome Widener Crunches Grizzlies • Sports Profile: Debbie Tweed • Cross Country Streak Alive • Despite 2-0 Loss, Booters Still Showing Promisehttps://digitalcommons.ursinus.edu/grizzlynews/1042/thumbnail.jp

A population of gamma-ray emitting globular clusters seen with the Fermi Large Area Telescope

Globular clusters with their large populations of millisecond pulsars (MSPs) are believed to be potential emitters of high-energy gamma-ray emission. Our goal is to constrain the millisecond pulsar populations in globular clusters from analysis of gamma-ray observations. We use 546 days of continuous sky-survey observations obtained with the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope to study the gamma-ray emission towards 13 globular clusters. Steady point-like high-energy gamma-ray emission has been significantly detected towards 8 globular clusters. Five of them (47 Tucanae, Omega Cen, NGC 6388, Terzan 5, and M 28) show hard spectral power indices $(0.7 < \Gamma <1.4)$ and clear evidence for an exponential cut-off in the range 1.0-2.6 GeV, which is the characteristic signature of magnetospheric emission from MSPs. Three of them (M 62, NGC 6440 and NGC 6652) also show hard spectral indices $(1.0 < \Gamma < 1.7)$, however the presence of an exponential cut-off can not be unambiguously established. Three of them (Omega Cen, NGC 6388, NGC 6652) have no known radio or X-ray MSPs yet still exhibit MSP spectral properties. From the observed gamma-ray luminosities, we estimate the total number of MSPs that is expected to be present in these globular clusters. We show that our estimates of the MSP population correlate with the stellar encounter rate and we estimate 2600-4700 MSPs in Galactic globular clusters, commensurate with previous estimates. The observation of high-energy gamma-ray emission from a globular cluster thus provides a reliable independent method to assess their millisecond pulsar populations that can be used to make constraints on the original neutron star X-ray binary population, essential for understanding the importance of binary systems in slowing the inevitable core collapse of globular clusters.Comment: Accepted for publication in A&A. Corresponding authors: J. Kn\"odlseder, N. Webb, B. Pancraz

Fermi Large Area Telescope Constraints on the Gamma-ray Opacity of the Universe

The Extragalactic Background Light (EBL) includes photons with wavelengths from ultraviolet to infrared, which are effective at attenuating gamma rays with energy above ~10 GeV during propagation from sources at cosmological distances. This results in a redshift- and energy-dependent attenuation of the gamma-ray flux of extragalactic sources such as blazars and Gamma-Ray Bursts (GRBs). The Large Area Telescope onboard Fermi detects a sample of gamma-ray blazars with redshift up to z~3, and GRBs with redshift up to z~4.3. Using photons above 10 GeV collected by Fermi over more than one year of observations for these sources, we investigate the effect of gamma-ray flux attenuation by the EBL. We place upper limits on the gamma-ray opacity of the Universe at various energies and redshifts, and compare this with predictions from well-known EBL models. We find that an EBL intensity in the optical-ultraviolet wavelengths as great as predicted by the "baseline" model of Stecker et al. (2006) can be ruled out with high confidence.Comment: 42 pages, 12 figures, accepted version (24 Aug.2010) for publication in ApJ; Contact authors: A. Bouvier, A. Chen, S. Raino, S. Razzaque, A. Reimer, L.C. Reye