3,455 research outputs found
Non-gaussianities and the Stimulated creation of quanta in the inflationary universe
Cosmological inflation generates a spectrum of density perturbations that can
seed the cosmic structures we observe today. These perturbations are usually
computed as the result of the gravitationally-induced spontaneous creation of
perturbations from an initial vacuum state. In this paper, we compute the
perturbations arising from gravitationally-induced stimulated creation when
perturbations are already present in the initial state. The effect of these
initial perturbations is not diluted by inflation and survives to its end, and
beyond. We consider a generic statistical density operator describing an
initial mixed state that includes probabilities for nonzero numbers of scalar
perturbations to be present at early times during inflation. We analyze the
primordial bispectrum for general configurations of the three different
momentum vectors in its arguments. We find that the initial presence of quanta
can significantly enhance non-gaussianities in the so-called squeezed limit.
Our results show that an observation of non-gaussianities in the squeezed limit
can occur for single-field inflation when the state in the very early
inflationary universe is not the vacuum, but instead contains early-time
perturbations. Valuable information about the initial state can then be
obtained from observations of those non-gaussianities.Comment: 25 page
Mixed-state twin observables
Twin observables, i.e. opposite subsystem observables A+ and A- that are
indistinguishable in measurement in a given mixed or pure state W, are
investigated in detail algebraicly and geometrically. It is shown that there is
a far-reaching correspondence between the detectable (in W) spectral entities
of the two operators. Twin observables are state-dependently quantum-logically
equivalent, and direct subsystem measurement of one of them ipso facto gives
rise to the indirect (i.e. distant) measurement of the other. Existence of
nontrivial twins requires singularity of W. Systems in thermodynamic
equilibrium do not admit subsystem twins. These observables may enable one to
simplify the matrix representing W.Comment: 13 page
Transnational knowledge in social work programs : challenges and strategies within assisted voluntary return and reintegration support
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Oligonucleotide compound and method for treating nidovirus infections
A method and oligonucleotide compound for inhibiting replication of a nidovirus in virus-infected animal cells are disclosed. The compound (i) has a nuclease-resistant backbone, (ii) is capable of uptake by the infected cells, (iii) contains between 8-25 nucleotide bases, and (iv) has a sequence capable of disrupting base pairing between the transcriptional regulatory sequences in the 5′ leader region of the positive-strand viral genome and negative-strand 3′ subgenomic region. In practicing the method, infected cells are exposed to the compound in an amount effective to inhibit viral replication
Clustering of eating disorder symptoms in a general population female twin sample: A latent class analysis
Characteristics of tropospheric ozone depletion events in the Arctic spring: analysis of the ARCTAS, ARCPAC, and ARCIONS measurements and satellite BrO observations
Arctic ozone depletion events (ODEs) are caused by halogen catalyzed ozone loss. In situ chemistry, advection of ozone-poor air mass, and vertical mixing in the lower troposphere are important factors affecting ODEs. To better characterize the ODEs, we analyze the combined set of surface, ozonesonde, and aircraft in situ measurements of ozone and bromine compounds during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS), the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC), and the Arctic Intensive Ozonesonde Network Study (ARCIONS) experiments (April 2008). Tropospheric BrO columns retrieved from satellite measurements and back trajectory calculations are also used to investigate the characteristics of observed ODEs. In situ observations from these field experiments are inadequate to validate tropospheric BrO columns derived from satellite measurements. In view of this difficulty, we construct an ensemble of tropospheric column BrO estimates from two satellite (OMI and GOME-2) measurements and with three independent methods of calculating stratospheric BrO columns. Furthermore, we select analysis methods that do not depend on the absolute magnitude of column BrO, such as time-lagged correlation analysis of ozone and tropospheric column BrO, to understand characteristics of ODEs. Time-lagged correlation analysis between in situ (surface and ozonesonde) measurements of ozone and satellite derived tropospheric BrO columns indicates that the ODEs are due to either local halogen-driven ozone loss or short-range (∼1 day) transport from nearby regions with ozone depletion. The effect of in situ ozone loss is also evident in the diurnal variation difference between low (10th and 25th percentiles) and higher percentiles of surface ozone concentrations at Alert, Canada. Aircraft observations indicate low-ozone air mass transported from adjacent high-BrO regions. Correlation analyses of ozone with potential temperature and time-lagged tropospheric BrO column show that the vertical extent of local ozone loss is surprisingly deep (1–2 km) at Resolute and Churchill, Canada. The unstable boundary layer during ODEs at Churchill could potentially provide a source of free-tropospheric BrO through convective transport and explain the significant negative correlation between free-tropospheric ozone and tropospheric BrO column at this site
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