Strings after D-term inflation: evolution and properties of chiral cosmic strings

We motivate the study of chiral cosmic strings through a scenario of structure formation which mixes D-term inflation and strings. We then discuss some properties of chiral cosmic strings, and results regarding their evolution and possible cosmological consequences are presented.Comment: 4 pages, 2 figures. To appear in the proceedings of the CAPP2000 conference held at Verbier, Switzerland between july 17th and 28th, 200

Translation invariant time-dependent solutions to massive gravity

Homogeneous time-dependent solutions of massive gravity generalise the plane wave solutions of the linearised Fierz-Pauli equations for a massive spin-two particle, as well as the Kasner solutions of General Relativity. We show that they also allow a clear counting of the degrees of freedom and represent a simplified framework to work out the constraints, the equations of motion and the initial value formulation. We work in the vielbein formulation of massive gravity, find the phase space resulting from the constraints and show that several disconnected sectors of solutions exist some of which are unstable. The initial values determine the sector to which a solution belongs. Classically, the theory is not pathological but quantum mechanically the theory may suffer from instabilities. The latter are not due to an extra ghost-like degree of freedom.Comment: 31 page

A formal introduction to Horndeski and Galileon theories and their generalizations

We review different constructions of Galileon theories in both flat and curved space, and for both single scalar field models as well as multi-field models. Our main emphasis is on the formal mathematical properties of these theories and their construction.Comment: 19 page

Translation invariant time-dependent solutions to massive gravity II

This paper is a sequel to arXiv:1310.6560 [hep-th] and is also devoted to translation-invariant solutions of ghost-free massive gravity in its moving frame formulation. Here we consider a mass term which is linear in the vielbein (corresponding to a $\beta_3$ term in the 4D metric formulation) in addition to the cosmological constant. We determine explicitly the constraints, and from the initial value formulation show that the time-dependent solutions can have singularities at a finite time. Although the constraints give, as in the $\beta_1$ case, the correct number of degrees of freedom for a massive spin two field, we show that the lapse function can change sign at a finite time causing a singular time evolution. This is very different to the $\beta_1$ case where time evolution is always well defined. We conclude that the $\beta_3$ mass term can be pathological and should be treated with care.Comment: 19 pages, 1 figur

On Tachyon kinks from the DBI action

We consider solitonic solutions of the DBI tachyon effective action for a non-BPS brane in the presence of an electric field. We find that for a constant electric field $\tilde E\le 1$, regular solitons compactified on a circle admit a singular and decompactified limit corresponding to Sen's proposal provided the tachyon potential satisfies some restrictions. On the other hand for the critical electric field $\tilde E=1$, regular and finite energy solitons are constructed without any restriction on the potential.Comment: proceedings of the second string phenomenology conference, Durham, 30th July to 4th August 200

The time dependence of muon spin relaxation spectra and spin correlation functions

The existing theory of the microscopic interpretation of the dynamical contribution to zero-field muon depolarization spectra in a longitudinal geometry is developed. The predicted relaxation of the muon depolarization is calculated from two forms of the spin correlation function. First, when the spin correlation function has an exponential form with a single wave vector dependent relaxation rate is considered, it is shown that this form of the spin correlation function reproduces the slow and fast fluctuation limits of stochastic spin theory regardless of the choice of microscopic spin model. Second, if the spin correlation function is a homogeneous scaling function (such as a power-law decay with time), as suggested by the mode-coupling theory of spin dynamics, this results in a stretched exponential relaxation of the muon spectra. For simple spin diffusion, the muon spectra are shown to be relax with a root-exponential form.Comment: 5 pages, 1 figur

Gravitational wave signatures from kink proliferation on cosmic (super-) strings

Junctions on cosmic string loops give rise to the proliferation of sharp kinks. We study the effect of this proliferation on the gravitational wave (GW) signals emitted from string networks with junctions, assuming a scaling solution. We calculate the rate of occurrence and the distribution in amplitude of the GW bursts emitted at cusps and kinks in the frequency bands of LIGO and LISA as a function of the string tension, the number of sharp kinks on loops with junctions and the fraction of loops in the cosmological network which have junctions. Combining our results with current observational constraints, we find that pulsar data rule out a significant number of kinks on loops for strings with tensions G\mu > 10^{-12}. By contrast, for smaller tensions current observations allow for a large number of kinks on loops. If this is the case, the incoherent superposition of small bursts emitted at kink-kink encounters leads to an enhanced GW background that hides the strong individual bursts from kinks and cusps.Comment: 32 pages, 13 figure

Cardiorespiratory fitness and aerobic performance adaptations to a 4-week sprint interval training in young healthy untrained females

Purpose: The aim of this study was to test the effects of sprint interval training (SIT) on cardiorespiratory fitness and aerobic performance measures in young females.Methods: Eight healthy, untrained females (age 21 ± 1 years; height 165 ± 5 cm; body mass 63 ± 6 kg) completed cycling peak oxygen uptake ( V˙O2V˙O2  peak), 10-km cycling time trial (TT) and critical power (CP) tests pre- and post-SIT. SIT protocol included 4 × 30-s “all-out” cycling efforts against 7 % body mass interspersed with 4 min of active recovery performed twice per week for 4 weeks (eight sessions in total).Results: There was no significant difference in  V˙O2V˙O2  peak following SIT compared to the control period (control period: 31.7 ± 3.0 ml kg−1 min−1; post-SIT: 30.9 ± 4.5 ml kg−1 min−1; p > 0.05), but SIT significantly improved time to exhaustion (TTE) (control period: 710 ± 101 s; post-SIT: 798 ± 127 s; p = 0.00), 10-km cycling TT (control period: 1055 ± 129 s; post-SIT: 997 ± 110 s; p = 0.004) and CP (control period: 1.8 ± 0.3 W kg−1; post-SIT: 2.3 ± 0.6 W kg−1; p = 0.01).Conclusions: These results demonstrate that young untrained females are responsive to SIT as measured by TTE, 10-km cycling TT and CP tests. However, eight sessions of SIT over 4 weeks are not enough to provide sufficient training stimulus to increase  V˙O2V˙O2  peak