42,158 research outputs found
Primordial Non-Gaussianity and Gravitational Waves: Observational Tests of Brane Inflation in String Theory
We study brane inflation scenarios in a warped throat geometry and show that
there exists a consistency condition between the non-Gaussianity of the
curvature perturbation and the amplitude and scale-dependence of the primordial
gravitational waves. This condition is independent of the warping of the throat
and the form of the inflaton potential. We find that such a relation could be
tested by a future CMB polarization experiment if the Planck satellite is able
to detect both a gravitational wave background and a non-Gaussian statistic. In
models where the observable stage of inflation occurs when the brane is in the
tip region of the throat, we derive a further consistency condition involving
the scalar spectral index, the tensor-scalar ratio and the curvature
perturbation bispectrum. We show that when such a relation is combined with the
WMAP3 results, it leads to a model-independent bound on the gravitational wave
amplitude given by 0.001 < r < 0.01. This corresponds to the range of
sensitivity of the next generation of CMB polarization experiments.Comment: 7 pages, uses RevTeX4. v2, replaced with version accepted by Phys.
Rev.
Primordial non-gaussianities from multiple-field inflation
We calculate the three-point correlation function evaluated at horizon
crossing for a set of interacting scalar fields coupled to gravity during
inflation. This provides the initial condition for the three-point function of
the curvature perturbation in the Sasaki--Stewart \delta N formulation. We find
that the effect is small, of the order of a slow-roll parameter, and that the
non-gaussianity can be determined on large scales once the unperturbed
background evolution is known. As an example of the use of our formalism, we
calculate the primordial non-gaussianity arising in a model of assisted
inflation.Comment: 24 pages, JCAP LaTeX style; replaced with version accepted by JCAP.
Some corrections to Sections 2 and 5, conclusions unchange
Primordial non-gaussianities in single field inflation
We calculate the three-point function for primordial scalar fluctuations in a
single field inflationary scenario where the scalar field Lagrangian is a
completely general function of the field and its first derivative. We obtain an
explicit expression for the three-point correlation function in a
self-consistent approximation scheme where the expansion rate varies slowly,
analogous to the slow-roll limit in standard, single-field inflation. The
three-point function can be written in terms of the familiar slow-roll
parameters and three new parameters which measure the non-trivial kinetic
structure of the scalar field, the departure of the sound speed from the speed
of light, and the rate of change of the sound speed.Comment: 26 pages, uses iopart.cls. Updated to match version published in JCA
The tension between gauge coupling unification, the Higgs boson mass, and a gauge-breaking origin of the supersymmetric mu-term
We investigate the possibility of generating the -term in the MSSM by
the condensation of a field that is a singlet under the SM gauge group but
charged under an additional family-independent gauge symmetry. We
attempt to do so while preserving the gauge coupling unification of the MSSM.
For this, we find that SM non-singlet exotics must be present in the spectrum.
We also prove that the pure anomalies can always be solved with
rationally charged fields, but that a large number of SM singlets are often
required. For charges that are consistent with an embedding of the
MSSM in SU(5) or SO(10), we show that the charges of the MSSM states
can always be expressed as a linear combination of abelian subgroups of .
However, the SM exotics do not appear to have a straightforward embedding into
GUT multiplets. We conclude from this study that if this approach to the
-term is correct, as experiment can probe, it will necessarily complicate
the standard picture of supersymmetric grand unification.Comment: 10 pages, no figure
Firmware Development Improves System Efficiency
Most manufacturing processes require physical pointwise positioning of the components or tools from one location to another. Typical mechanical systems utilize either stop-and-go or fixed feed-rate procession to accomplish the task. The first approach achieves positional accuracy but prolongs overall time and increases wear on the mechanical system. The second approach sustains the throughput but compromises positional accuracy. A computer firmware approach has been developed to optimize this point wise mechanism by utilizing programmable interrupt controls to synchronize engineering processes 'on the fly'. This principle has been implemented in an eddy current imaging system to demonstrate the improvement. Software programs were developed that enable a mechanical controller card to transmit interrupts to a system controller as a trigger signal to initiate an eddy current data acquisition routine. The advantages are: (1) optimized manufacturing processes, (2) increased throughput of the system, (3) improved positional accuracy, and (4) reduced wear and tear on the mechanical system
Lindstedt Series Solutions of the Fermi-Pasta-Ulam Lattice
We apply the Lindstedt method to the one dimensional Fermi-Pasta-Ulam
lattice to find fully general solutions to the complete set of equations of
motion. The pertubative scheme employed uses as the expansion
parameter, where is the coefficient of the quartic coupling between
nearest neighbors. We compare our non-secular perturbative solutions to
numerical solutions and find striking agreement.Comment: 17 pages, 10 figures. To appear in the Journal of Mathematical
Physic
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