4,261 research outputs found
Status of NINJA: the Numerical INJection Analysis project
The 2008 NRDA conference introduced the Numerical INJection Analysis project (NINJA), a new collaborative effort between the numerical relativity community and the data analysis community. NINJA focuses on modeling and searching for gravitational wave signatures from the coalescence of binary system of compact objects. We review the scope of this collaboration and the components of the first NINJA project, where numerical relativity groups shared waveforms and data analysis teams applied various techniques to detect them when embedded in colored Gaussian noise
Auto-Concealment of Supersymmetry in Extra Dimensions
In supersymmetric (SUSY) theories with extra dimensions the visible energy in
sparticle decays can be significantly reduced and its energy distribution
broadened, thus significantly weakening the present collider limits on SUSY.
The mechanism applies when the lightest supersymmetric particle (LSP) is a bulk
state-- e.g. a bulk modulino, axino, or gravitino-- the size of the extra
dimensions larger than ~ cm, and for a broad variety of visible
sparticle spectra. In such cases the lightest ordinary supersymmetric particle
(LOSP), necessarily a brane-localised state, decays to the Kaluza-Klein (KK)
discretuum of the LSP. This dynamically realises the compression mechanism for
hiding SUSY as decays into the more numerous heavier KK LSP states are favored.
We find LHC limits on right-handed slepton LOSPs evaporate, while LHC limits on
stop LOSPs weaken to ~350-410 GeV compared to ~700 GeV for a stop decaying to a
massless LSP. Similarly, for the searches we consider, present limits on direct
production of degenerate first and second generation squarks drop to ~450 GeV
compared to ~800 GeV for a squark decaying to a massless LSP. Auto-concealment
typically works for a fundamental gravitational scale of ~10-100 TeV, a
scale sufficiently high that traditional searches for signatures of extra
dimensions are mostly avoided. If superpartners are discovered, their prompt,
displaced, or stopped decays can also provide new search opportunities for
extra dimensions with the potential to reach ~ GeV. This mechanism
applies more generally than just SUSY theories, pertaining to any theory where
there is a discrete quantum number shared by both brane and bulk sectors.Comment: 22 pages, 13 figures. Minor changes to match published versio
The Gravitational Wave Signature of Core-Collapse Supernovae
We review the ensemble of anticipated gravitational-wave (GW) emission
processes in stellar core collapse and postbounce core-collapse supernova
evolution. We discuss recent progress in the modeling of these processes and
summarize most recent GW signal estimates. In addition, we present new results
on the GW emission from postbounce convective overturn and protoneutron star
g-mode pulsations based on axisymmetric radiation-hydrodynamic calculations.
Galactic core-collapse supernovae are very rare events, but within 3-5 Mpc from
Earth, the rate jumps to 1 in ~2 years. Using the set of currently available
theoretical gravitational waveforms, we compute upper-limit optimal
signal-to-noise ratios based on current and advanced LIGO/GEO600/VIRGO noise
curves for the recent SN 2008bk which exploded at ~3.9 Mpc. While initial LIGOs
cannot detect GWs emitted by core-collapse events at such a distance, we find
that advanced LIGO-class detectors could put significant upper limits on the GW
emission strength for such events. We study the potential occurrence of the
various GW emission processes in particular supernova explosion scenarios and
argue that the GW signatures of neutrino-driven, magneto-rotational, and
acoustically-driven core-collapse SNe may be mutually exclusive. We suggest
that even initial LIGOs could distinguish these explosion mechanisms based on
the detection (or non-detection) of GWs from a galactic core-collapse
supernova.Comment: Topical Review, accepted for publication in CQG. 51 pages, 13
figures, a version of the article with high-resolution figures is available
from http://stellarcollapse.org/papers/Ott_SN_GW_review2008.pdf. Update:
Added section on core collapse simulations and the treatment of general
relativit
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