8,478 research outputs found
CMB Constraints on Principal Components of the Inflaton Potential
We place functional constraints on the shape of the inflaton potential from
the cosmic microwave background through a variant of the generalized slow roll
approximation that allows large amplitude, rapidly changing deviations from
scale-free conditions. Employing a principal component decomposition of the
source function G'~3(V'/V)^2 - 2V''/V and keeping only those measured to better
than 10% results in 5 nearly independent Gaussian constraints that maybe used
to test any single-field inflationary model where such deviations are expected.
The first component implies < 3% variations at the 100 Mpc scale. One component
shows a 95% CL preference for deviations around the 300 Mpc scale at the ~10%
level but the global significance is reduced considering the 5 components
examined. This deviation also requires a change in the cold dark matter density
which in a flat LCDM model is disfavored by current supernova and Hubble
constant data and can be tested with future polarization or high multipole
temperature data. Its impact resembles a local running of the tilt from
multipoles 30-800 but is only marginally consistent with a constant running
beyond this range. For this analysis, we have implemented a ~40x faster WMAP7
likelihood method which we have made publicly available.Comment: 12 pages, 14 figures, submitted to Phys.Rev.D. Optimized WMAP7
likelihood code and principal component functions of the GSR source function
available at http://background.uchicago.edu/wmap_fast
A polyphonic acoustic vortex and its complementary chords
Using an annular phased array of eight loudspeakers, we generate sound beams that simultaneously contain phase singularities at a number of different frequencies. These frequencies correspond to different musical notes and the singularities can be set to overlap along the beam axis, creating a polyphonic acoustic vortex. Perturbing the drive amplitudes of the speakers means that the singularities no longer overlap, each note being nulled at a slightly different lateral position, where the volume of the other notes is now nonzero. The remaining notes form a tri-note chord. We contrast this acoustic phenomenon to the optical case where the perturbation of a white light vortex leads to a spectral spatial distribution
The effect of external forces on discrete motion within holographic optical tweezers
Holographic optical tweezers is a widely used technique to manipulate the individual positions of optically trapped micron-sized particles in a sample. The trap positions are changed by updating the holographic image displayed on a spatial light modulator. The updating process takes a finite time, resulting in a temporary decrease of the intensity, and thus the stiffness, of the optical trap. We have investigated this change in trap stiffness during the updating process by studying the motion of an optically trapped particle in a fluid flow. We found a highly nonlinear behavior of the change in trap stiffness vs. changes in step size. For step sizes up to approximately 300 nm the trap stiffness is decreasing. Above 300 nm the change in trap stiffness remains constant for all step sizes up to one particle radius. This information is crucial for optical force measurements using holographic optical tweezers
Violation of Leggett inequalities in orbital angular momentum subspaces
We report an experimental test of Leggett's non-local hidden variable theory in an orbital angular momentum (OAM) state space of light. We show that the correlations we observe are in conflict with Leggett's model, thus excluding a particular class of non-local hidden variable theories for the first time in a non-polarization state space. It is known that the violation of the Leggett inequality becomes stronger as more detection settings are used. The required measurements become feasible in an OAM subspace, and we demonstrate this by testing the inequality using three and four settings. We observe excellent agreement with quantum predictions and a violation of five and six standard deviations, respectively, compared to Leggett's non-local hidden variable theory
Taking charge of one's feelings: Sense of power and affect regulation
People who are good at regulating their feelings benefit from more desirable affective lives. Here we examine whether individual differences in chronic feelings of power are associated with regulatory efforts aimed at maintaining positive affect and ceasing negative affect. In Study 1, we found that people with a stronger (vs. weaker) sense of power were more inclined to cognitively re-frame (reappraise) and up-regulate (repair) their affective experiences, whilst also being less inclined to suppress their feelings. Drawing on affective experiences sampled repeatedly over a one-week period, in Study 2 we found that people with a stronger (vs. weaker) sense of power were more likely to cease their negative affect. However, a stronger (vs. weaker) sense of power was not associated with the likelihood to maintain positive affect. Together, the findings highlight a novel domain in which power may enhance self-regulation, and help explain how power differentials shape people’s affective and social lives
From grumpy to cheerful (and back): How power impacts mood in and across different contexts
Although lay intuition and some academic theories suggest that power increases variability in mood, the prevailing view in the literature is that power elevates mood—a view that is not consistently borne out in empirical data. To rectify these discrepancies, we conducted five studies examining the impact of high and low power on mood in, and across, contexts of differing valence (negative vs. neutral vs. positive). Drawing on 19,710 observations from 1,042 participants, we found that high (vs. medium/control) power elevated, and low (vs. medium/control) power dampened, individuals' mood at baseline/in neutral contexts and in positive contexts. However, neither high (vs. medium/control) power nor low (vs. medium/control) power modulated individuals' mood in negative contexts. Overall, high (vs. medium/control) power tended to increase, and low (vs. medium/control) power decreased variability in mood across contexts (the former effect was marginally significant). We discuss how these findings corroborate, but also qualify, lay intuition and social psychological theories of power
When smiles (and frowns) speak words: Does power impact the correspondence between self-reported affect and facial expressions?
Self-reported experiences are often poor indicators of outward expressions. Here we examine social power as a variable that may impact the relationship between self-reported affect and facial expressions. Earlier studies addressing this issue were limited by focusing on a single facial expression (smiling) and by using different, less sensitive methods that yielded mostly null results. Sampling, for the first time, self-reported affect repeatedly in response to different negative, neutral and positive stimuli, and measuring concurrent facial muscle activation via electromyography, we found that high power (vs. baseline) increased the correspondence between self-reported positive affect and smiling. There was also an indication that high power (vs. baseline) bolstered the association between self-reported negative affect and frowning but the effect did not pass more stringent criteria for significance (p ≤ .005) and was therefore deemed inconclusive. The prediction that low power (vs. baseline) decreases the correspondence between self-reported affect and smiling and frowning facial expressions was not supported. Taken together, it would appear that (high) power can impact the relationship between self-reported affect and facial expressions, but it remains to be seen whether this effect extends beyond smiling facial expressions
Analytic Behaviour of Competition among Three Species
We analyse the classical model of competition between three species studied
by May and Leonard ({\it SIAM J Appl Math} \textbf{29} (1975) 243-256) with the
approaches of singularity analysis and symmetry analysis to identify values of
the parameters for which the system is integrable. We observe some striking
relations between critical values arising from the approach of dynamical
systems and the singularity and symmetry analyses.Comment: 14 pages, to appear in Journal of Nonlinear Mathematical Physic
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