624 research outputs found
Strongly Scale-dependent Non-Gaussianity
We discuss models of primordial density perturbations where the
non-Gaussianity is strongly scale-dependent. In particular, the non-Gaussianity
may have a sharp cut-off and be very suppressed on large cosmological scales,
but sizeable on small scales. This may have an impact on probes of
non-Gaussianity in the large-scale structure and in the cosmic microwave
background radiation anisotropies.Comment: 4 page
Camp Oglethorpe: Maconâs Unknown Civil War Prisoner of War Camp, 1862-1864
Located along the Ocmulgee River, Macon, Georgia, is known for its International Cherry Blossom Festival, the Ocmulgee National Monument, Mercer University, among other historic and cultural sites. Yet, as Stephen Hoy and William Smith argue in Camp Oglethorpe: Maconâs Unknown Civil War Prisoner of War Camp, 1862-1864, Macon is not known for having been the site of a prisoner of war (POW) camp during the American Civil War. Both long-time residents of Macon, Hoy and Smith recognized that they were living within minutes of an important site that had long since faded from public memory. Taking advantage of their location and the hundreds of accounts written by Union POWs, the authors resolved to bring Camp Oglethorpe out of the shadow of Andersonville and other more infamous Civil War prisons to present this clearly-written and well-researched study of Maconâs âunknown prisoner of war camp.
Crossing the Deadlines: Civil War Prisons Reconsidered
In the volumeâs foreword, John T. Hubbell, professor emeritus at Kent State University, succinctly summarized the historiography of Civil War prisons, remarking, âIt seems that prisons and prisoners have beenâŠa part of the narrative, yet somehow strangely apart from it.â Seeking to remedy this disconnect, Michael P. Gray, author of The Business of Captivity: Elmira and its Civil War Prisons (2001), tasked eight scholars to âreconsiderâ Civil War prisons and prisoners of war (POWs) and scholarsâ interpretations of the topic. The result, Crossing the Deadlines: Civil War Prisons Reconsidered, is an enlightening essay collection that highlights the latest methodologies and interdisciplinary approaches to the topic of Civil War imprisonment and its place in the warâs narrative and public memory of the conflict
Production of Massive Fermions at Preheating and Leptogenesis
We present a complete computation of the inflaton decay into very massive
fermions during preheating. We show that heavy fermions are produced very
efficiently up to masses of order 10^{17}-10^{18} GeV; the accessible mass
range is thus even broader than the one for heavy bosons. We apply our findings
to the leptogenesis scenario, proposing a new version of it, in which the
massive right-handed neutrinos, responsible for the generation of the baryon
asymmetry, are produced during preheating. We also discuss other production
mechanisms of right-handed neutrinos in the early Universe, identifying the
neutrino mass parameters for which the observed baryon asymmetry is reproduced.Comment: 29 pages, 4 figure
The Lightest Higgs Boson Mass in the Minimal Supersymmetric Standard Model
We compute the upper bound on the mass of the lightest Higgs boson in the
Minimal Supersymmetric Standard Model in a model-independent way, including
leading (one-loop) and next-to-leading order (two-loop) radiative corrections.
We find that (contrary to some recent claims) the two-loop corrections are
negative with respect to the one-loop result and relatively small (\simlt
3\%). After defining physical (pole) top quark mass , by including QCD
self-energies, and physical Higgs mass , by including the electroweak
self-energies , we obtain the upper limit on
as a function of supersymmetric parameters. We include as supersymmetric
parameters the scale of supersymmetry breaking , the value of
and the mixing between stops (which is responsible
for the threshold correction on the Higgs quartic coupling). Our results do not
depend on further details of the supersymmetric model. In particular, for
TeV, maximal threshold effect and any value of
, we find GeV for GeV. In the particular
scenario where the top is in its infrared fixed point we find GeV
for GeV.Comment: 24 pages + 15 figures in one compressed uuencoded tarred postscript
file (The figures can be obtained by e-mail from [email protected]; also,
the whole postscript file of the text including the figures can be obtained
by ANONYMOUS FTP from ROCA.CSIC.ES (161.111.20.20) at the directory HEP the
file being HIGGS.PS: just type GET HEP/HIGGS.PS), Latex, CERN-TH.7334/9
The Sphaleron in a Magnetic Field and Electroweak Baryogenesis
The presence of a primordial magnetic field in the early universe affects the
dynamic of the electroweak phase transition enhancing its strength. This effect
may enlarge the window for electroweak baryogenesis in the minimal
supersymmetric extension of the standard model or even resurrect the
electroweak baryogenesis scenario in the standard model. We compute the
sphaleron energy in the background of the magnetic field and show that, due to
the sphaleron dipole moment, the barrier between topologically inequivalent
vacua is lowered. Therefore, the preservation of the baryon asymmetry calls for
a much stronger phase transition than required in the absence of a magnetic
field. We show that this effect overwhelms the gain in the phase transition
strength, and conclude that magnetic fields do not help electroweak
baryogenesis.Comment: 10 pages, 2 figure
Testing Primordial Black Holes as Dark Matter through LISA
The idea that primordial black holes (PBHs) can comprise most of the dark
matter of the universe has recently reacquired a lot of momentum. Observational
constraints, however, rule out this possibility for most of the PBH masses,
with a notable exception around . These light PBHs may be
originated when a sizeable comoving curvature perturbation generated during
inflation re-enters the horizon during the radiation phase. During such a
stage, it is unavoidable that gravitational waves (GWs) are generated. Since
their source is quadratic in the curvature perturbations, these GWs are
generated fully non-Gaussian. Their frequency today is about the mHz, which is
exactly the range where the LISA mission has the maximum of its sensitivity.
This is certainly an impressive coincidence. We show that this scenario of PBHs
as dark matter can be tested by LISA by measuring the GW two-point correlator.
On the other hand, we show that the short observation time (as compared to the
age of the universe) and propagation effects of the GWs across the perturbed
universe from the production point to the LISA detector suppress the bispectrum
to an unobservable level. This suppression is completely general and not
specific to our model.Comment: 22 pages, 12 figures. v3: matching published versio
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