Miracle-dz/UniFAR-FTUs huggingface dataset:
Cosmological Asymptotics in Higher-Order Gravity Theories

We study the early-time behavior of isotropic and homogeneous solutions in vacuum as well as radiation-filled cosmological models in the full, effective, four dimensional gravity theory with higher derivatives. We use asymptotic methods to analyze all possible ways of approach to the initial singularity of such universes. In order to do so, we construct autonomous dynamical systems that describe the evolution of these models, and decompose the associated vector fields. We prove that, at early times, all flat vacua as well as general curved ones are globally attracted by the "universal" square root scaling solution. Open vacua, on the other hand show in both, future and past directions a dominant asymptotic approach to horizon-free, Milne states that emerge from initial data sets of smaller dimension. Closed universes exhibit more complex logarithmic singularities. Our results on asymptotic stability show a possible relation to cyclic and ekpyrotic cosmologies at the passage through the singularity. In the case of radiation-filled universes of the same class we show the essential uniqueness and stability of the resulting asymptotic scheme, once more dominated by $t^{1/2}$, in all cases except perhaps that of the conformally invariant Bach-Weyl gravity. In all cases, we construct a formal series representation valid near the initial singularity of the general solution of these models and prove that curvature as well as radiation play a subdominant role in the dominating form. A discussion is also made on the implications of these results for the generic initial state of the theory.
Low-Mass Dark-Matter Hint from CDMS II, Higgs Boson at the LHC, and Darkon Models

The CDMS II experiment has observed three events which may have arisen from weakly interacting massive particle (WIMP) dark matter (DM) with mass of order 9 GeV colliding with nuclei. Although the implied WIMP parameter region seems to be excluded by limits from the XENON experiments, it is interesting that most of this tension can go away if the WIMP-nucleon interaction violates isospin. This motivates us to explore some of the implications for models in which a real gauge-singlet scalar particle, the darkon, serves as the WIMP, taking into account the recent discovery of a Higgs boson at the LHC and Planck determination of the DM relic density. In the simplest scenario, involving only the standard model plus a darkon, the Higgs boson is largely invisible due to its decay into a pair of darkons having the WIMP mass suggested by CDMS II and hence cannot be identified with the one found at the LHC. We find, on the other hand, that a two-Higgs-doublet model supplemented with a darkon has ample parameter space to accommodate well both the new potential DM hint from CDMS II and the Higgs data from the LHC, whether or not the darkon-nucleon interaction conserves isospin.
Comments on string theory backgrounds with non-relativistic conformal symmetry

We consider non-relativistic conformal quantum mechanical theories that arise by doing discrete light cone quantization of field theories. If the field theory has a gravity dual, then the conformal quantum mechanical theory can have a gravity dual description in a suitable finite temperature and finite density regime. Using this we compute the thermodynamic properties of the system. We give an explicit example where we display both the conformal quantum mechanical theory as well as the gravity dual. We also discuss the string theory embedding of certain backgrounds with non-relativistic conformal symmetry that were recently discussed. Using this, we construct finite temperature and finite density solutions, with asymptotic non-relativistic conformal symmetry. In addition, we derive consistent Kaluza-Klein truncations of type IIB supergravity to a five dimensional theory with massive vector fields.
Spin-torque driven magnetic vortex self-oscillations in perpendicular magnetic fields

We have employed complete micromagnetic simulations to analyze dc current driven self-oscillations of a vortex core in a spin-valve nanopillar in a perpendicular field by including the coupled effect of the spin-torque and the magnetostatic field computed self-consistently for the entire spin-valve. The vortex in the thicker nanomagnet moves along a quasielliptical trajectory that expands with applied current, resulting in “blueshifting” of the frequency, while the magnetization of the thinner nanomagnet is nonuniform due to the bias current. The simulations explain the experimental magnetoresistance-field hysteresis loop and yield good agreement with the measured frequency versus current behavior of this spin-torque vortex oscillator.
Symmetric Device-Independent Quantum Key Distribution Against General Attack

A symmetric device-independent quantum key distribution (DIQKD) protocol is proposed in this paper, with Holevo limit and subadditivity of von Neumann entropy, one can bound Eve's ability with collective attack. Together with symmetry of this protocol, the state Eve prepared for Alice and Bob, and at the same time, her eavesdropping on Alice's and Bob's measurements can be definitely inferred at the assumption that Eve aims at maximizing her information gain. The optimal state under this circumstance can be solely bounded with Alice and Bob's statistical results on the quantity of Clauser-Horne-Shimony-Holt (CHSH) polynomial $S$, that is, our symmetric DIQKD has the same secure basis as that of Ekert91 protocol.
X-ray eclipse time delays in 4U 2129+47

Aims. 4U 2129+47 was discovered in the early 80’s and classified as an accretion disk corona source due to its broad and partial X-ray eclipses. The 5.24 h binary orbital period was inferred from the X-ray and optical light curve modulation, implying a late K or M spectral type companion star. The source entered a low state in 1983, during which the optical modulation disappeared and an F8 IV star was revealed, suggesting that 4U 2129+47 might be part of a triple system. The nature of 4U 2129+47 has since been investigated, but no definitive conclusion has been reached. Methods. Here, we present timing and spectral analyses of two XMM-Newton observations of this source, carried out in May and June, 2005. Results. We find evidence for a delay between two mid-eclipse epochs measured ∼22 days apart, and we show that this delay can be naturally explained as being due to the orbital motion of the binary 4U 2129+47 around the center of mass of a triple system. This result thus provides further support in favor of the triple nature of 4U 2129+47.
Wormhole on DGP brane

We analyze a spacetime structure on a new brane configuration constructed recently in the Dvali-Gabadadze-Porrati braneworld context. The brane, embedded on a five-dimensional bubble of nothing, has a wormhole structure. It is an exact solution without any matter fields, and thus the energy conditions for matter fields are trivially satisfied. We see that, under the traversability condition, the size of the bubble should be larger than 10^{10}cm or so.
Low angular momentum flow model of Sgr A* activity

Sgr A* is the closest massive black hole and can be observed with the highest angular resolution. Nevertheless, our current understanding of the accretion process in this source is very poor. The inflow is almost certainly of low radiative efficiency and it is accompanied by a strong outflow and the flow is strongly variable but the details of the dynamics are unknown. Even the amount of angular momentum in the flow is an open question. Here we argue that low angular momentum scenario is better suited to explain the flow variability. We present a new hybrid model which describes such a flow and consists of an outer spherically symmetric Bondi flow and an inner axially symmetric flow described through MHD simulations. The assumed angular momentum of the matter is low, i.e. the corresponding circularization radius in the equatorial plane of the flow is just above the innermost stable circular orbit in pseudo-Newtonian potential. We compare the radiation spectrum from such a flow to the broad band observational data for Sgr A*.
Unraveling the Universe with DESI.

The Dark Energy Spectroscopic Instrument (DESI) is a stage IV ground-based dark energy experiment planned to begin operations in 2020. In this article, we provided a short review of DESI presented during the conference {\it Recontres de Moriond 2018}. DESI will use four different tracers for mapping the universe: from redshift 0.05 up to redshift 1.7 with galaxies and from 2.1 to 3.5 using quasars. DESI will measure a total of 35 million spectra covering regions of universe never explored before, providing a map of large scale structure that will enable major advances in the investigation of cosmic acceleration. The key science goals for DESI are to constrain dark energy and potential deviations of General Relativity using two complementary observables: the Baryonic Acoustic Oscillations (BAO) and the Redshift Space Distortions (RSD). Additional science goals, such as constraining the sum of neutrino masses and inflation, are expected with the baseline project. DESI installation started on February 2018 and the current construction of the instrument is on track. The imaging surveys that will serve to determine the targets are currently in the final stages, having achieved 80\% completion, and are expected to be finalized by the end of 2018. The DESI Collaboration is actively preparing for survey operations and science analysis, to be ready for the first light in January 2020.
THE PANCHROMATIC HUBBLE ANDROMEDA TREASURY. IV. A PROBABILISTIC APPROACH TO INFERRING THE HIGH-MASS STELLAR INITIAL MASS FUNCTION AND OTHER POWER-LAW FUNCTIONS

We present a probabilistic approach for inferring the parameters of the present-day power-law stellar mass function (MF) of a resolved young star cluster. This technique (1) fully exploits the information content of a given data set; (2) can account for observational uncertainties in a straightforward way; (3) assigns meaningful uncertainties to the inferred parameters; (4) avoids the pitfalls associated with binning data; and (5) can be applied to virtually any resolved young cluster, laying the groundwork for a systematic study of the high-mass stellar MF (M ≳ 1 M☉). Using simulated clusters and Markov Chain Monte Carlo sampling of the probability distribution functions, we show that estimates of the MF slope, α, are unbiased and that the uncertainty, Δα, depends primarily on the number of observed stars and on the range of stellar masses they span, assuming that the uncertainties on individual masses and the completeness are both well characterized. Using idealized mock data, we compute the theoretical precision, i.e., lower limits, on α, and provide an analytic approximation for Δα as a function of the observed number of stars and mass range. Comparison with literature studies shows that ∼3/4 of quoted uncertainties are smaller than the theoretical lower limit. By correcting these uncertainties to the theoretical lower limits, we find that the literature studies yield 〈α〉 = 2.46, with a 1σ dispersion of 0.35 dex. We verify that it is impossible for a power-law MF to obtain meaningful constraints on the upper mass limit of the initial mass function, beyond the lower bound of the most massive star actually observed. We show that avoiding substantial biases in the MF slope requires (1) including the MF as a prior when deriving individual stellar mass estimates, (2) modeling the uncertainties in the individual stellar masses, and (3) fully characterizing and then explicitly modeling the completeness for stars of a given mass. The precision on MF slope recovery in this paper are lower limits, as we do not explicitly consider all possible sources of uncertainty, including dynamical effects (e.g., mass segregation), unresolved binaries, and non-coeval populations. We briefly discuss how each of these effects can be incorporated into extensions of the present framework. Finally, we emphasize that the technique and lessons learned are applicable to more general problems involving power-law fitting.
Cosmological constant problem and renormalized vacuum energy density in curved background

The current vacuum energy density observed as dark energy ρdark≃ 2.5×10−47 GeV4 is unacceptably small compared with any other scales. Therefore, we encounter serious fine-tuning problem and theoretical difficulty to derive the dark energy. However, the theoretically attractive scenario has been proposed and discussed in literature: in terms of the renormalization-group (RG) running of the cosmological constant, the vacuum energy density can be expressed as ρvacuum≃ m2H2 where m is the mass of the scalar field and rather dynamical in curved spacetime. However, there has been no rigorous proof to derive this expression and there are some criticisms about the physical interpretation of the RG running cosmological constant. In the present paper, we revisit the RG running effects of the cosmological constant and investigate the renormalized vacuum energy density in curved spacetime. We demonstrate that the vacuum energy density described by ρvacuum≃ m2H2 appears as quantum effects of the curved background rather than the running effects of cosmological constant. Comparing to cosmological observational data, we obtain an upper bound on the mass of the scalar fields to be smaller than the Planck mass, m ≲ MPl.
ON THE ORIGIN OF THE SLOW SPEED SOLAR WIND: HELIUM ABUNDANCE VARIATIONS

The first ionization potential (FIP) effect is the by now well-known enhancement in abundance over photospheric values of Fe and other elements with FIP below about 10 eV observed in the solar corona and slow speed solar wind. In our model, this fractionation is achieved by means of the ponderomotive force, arising as Alfvén waves propagate through or reflect from steep density gradients in the solar chromosphere. This is also the region where low FIP elements are ionized, and high FIP elements are largely neutral leading to the fractionation as ions interact with the waves but neutrals do not. Helium, the element with the highest FIP and consequently the last to remain neutral as one moves upward, can be depleted in such models. Here, we investigate this depletion for varying loop lengths and magnetic field strengths. Variations in this depletion arise as the concentration of the ponderomotive force at the top of the chromosphere varies in response to Alfvén wave frequency with respect to the resonant frequency of the overlying coronal loop, the magnetic field, and possibly also the loop length. We find that stronger depletions of He are obtained for weaker magnetic field, at frequencies close to or just above the loop resonance. These results may have relevance to observed variations of the slow wind solar He abundance with wind speed, with slower slow speed solar wind having a stronger depletion of He.
Ground-state 12CO emission and a resolved jet at 115 GHz (rest frame) in the radio-loud quasar 3C 318

An analysis of 44 GHz VLA observations of the z = 1.574 radio-loud quasar 3C318 has revealed emission from the redshifted J = 1 - 0 transition of the CO molecule and spatially resolved the 6.3 kpc radio jet associated with the quasar at 115 GHz rest-frame. The continuum-subtracted line emitter is spatially offset from the quasar nucleus by 0.33" (2.82 kpc in projection). This spatial offset has a significance of >8-sigma and, together with a previously published -400 km/s velocity offset measured in the J = 2 - 1 CO line relative to the systemic redshift of the quasar, rules out a circumnuclear starburst or molecular gas ring and suggests that the quasar host galaxy is either undergoing a major merger with a gas-rich galaxy or is otherwise a highly disrupted system. If the merger scenario is correct then the event may be in its early stages, acting as the trigger for both the young radio jets in the quasar and a starburst in the merging galaxy. The total molecular gas mass in the spatially offset line emitter as measured from the ground-state CO line M_H2 = 3.7 (+/-0.4) x 10^10 (alpha_CO/0.8) M_solar. Assuming that the line-emitter can be modelled as a rotating disk, an inclination-dependent upper limit is derived for its dynamical mass M_dyn sin^2(i) < 3.2 x 10^9 M_solar, suggesting that for M_H2 to remain less than M_dyn the inclination angle must be i < 16 degrees. The far infrared and CO luminosities of 246 extragalactic systems are collated from the literature for comparison. The high molecular gas content of 3C318 is consistent with that of the general population of high redshift quasars and sub-millimetre galaxies.
Measurements of the coupling between the tumbling of rods and the velocity gradient tensor in turbulence

Abstract We present simultaneous experimental measurements of the dynamics of anisotropic particles transported by a turbulent flow and the velocity gradient tensor of the flow surrounding them. We track both rod-shaped particles and small spherical flow tracers using stereoscopic particle tracking. By using scanned illumination, we are able to obtain a high enough seeding density of tracers to measure the full velocity gradient tensor near the rod. The alignment of rods with the vorticity and the eigenvectors of the strain rate from experimental results agree well with numerical findings. A full description of the tumbling of rods in turbulence requires specifying a seven-dimensional joint probability density function (jPDF) of five scalars characterizing the velocity gradient tensor and two scalars describing the relative orientation of the rod. If these seven parameters are known, then Jeffery’s equation specifies the rod tumbling rate and any statistic of rod rotations can be obtained as a weighted average over the jPDF. To look for a lower-dimensional projection to simplify the problem, we explore conditional averages of the mean-squared tumbling rate. The conditional dependence of the mean-squared tumbling rate on the magnitude of both the vorticity and the strain rate is strong, as expected, and similar. There is also a strong dependence on the orientation between the rod and the vorticity, since a rod aligned with the vorticity vector tumbles due to strain but not vorticity. When conditioned on the alignment of the rod with the eigenvectors of the strain rate, the largest tumbling rate is obtained when the rod is oriented at a certain angle to the eigenvector that corresponds to the smallest eigenvalue, because this particular orientation maximizes the contribution from both the vorticity and strain.
An in- and ex-situ TEM study into the oxidisation of titanium (IV) sulphide

The degradation of liquid dispersed titanium (IV) sulphide (TiS$_2$) is studied from the point of view of oxidisation. TiS$_2$ is a layered two-dimensional nanomaterial, with potential for energy storage applications. However, flakes in dispersion were observed to degrade. We examined two oxidisation routes: deionised water at room temperature and oxygen gas within the temperature range 150-350{\deg}C. Water was seen to slowly oxidise flakes inwards from the edge, forming an amorphous oxide, a result comparable to the state of flakes which degraded within the original dispersion. Oxygen gas was seen to rapidly oxidise entire flakes to a polycrystalline oxide, when heated 275 {\deg}C and above. Degradation was studied with scanning transmission electron microscopy (STEM), energy dispersed x-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS). Density Functional Theory calculations have shown oxidisation by both water and gas molecules to be thermodynamically favourable.
Black holes, compact objects and solar system tests in non-relativistic general covariant theory of gravity

We study spherically symmetric static spacetimes generally filled with an anisotropic fluid in the nonrelativistic general covariant theory of gravity. In particular, we find that the vacuum solutions are not unique, and can be expressed in terms of the $U(1)$ gauge field $A$. When solar system tests are considered, severe constraints on $A$ are obtained, which seemingly pick up the Schwarzschild solution uniquely. In contrast to other versions of the Horava-Lifshitz theory, non-singular static stars made of a perfect fluid without heat flow can be constructed, due to the coupling of the fluid with the gauge field. These include the solutions with a constant pressure. We also study the general junction conditions across the surface of a star. In general, the conditions allow the existence of a thin matter shell on the surface. When applying these conditions to the perfect fluid solutions with the vacuum ones as describing their external spacetimes, we find explicitly the matching conditions in terms of the parameters appearing in the solutions. Such matching is possible even without the presence of a thin matter shell.
A Review on the Use of Letrozole in Female and Male Infertility

Infertility in developing countries is a distinct and complex problem that disproportionately affects women. Though not a physically restraining disease, it causes a huge social burden on the emotional, financial, and psychosocial quotients of those who suffer from it. Assisted reproductive procedures are frequently used to treat infertility. Years ago, the emergence of ovulation induction represented a significant advancement in treating female infertility. Letrozole, an aromatase inhibitor, is a potential therapy for ovulation induction. Numerous clinical conditions, including anovulatory infertility, polycystic ovarian syndrome, unexplained infertility, and early stages of endometriosis-related infertility, as well as many with improved live birth rates, have been proven to benefit from letrozole treatment. Letrozole is a superior alternative to the widely utilized ovulation induction with clomiphene citrate. While clomiphene citrate has certain limitations, letrozole successfully overcomes these limitations because of its lack of prolonged anti-estrogenic activity, short half-life, and lack of estrogen receptor activation. In most cases, this results in mono-follicular development and excellent live birth rates. According to the most recent research, letrozole can be used as the first-line therapy to treat infertility caused by polycystic ovarian syndrome and other causes. Letrozole is also emerging as a possible treatment for male infertility of unknown cause, proving to be an effective way of influencing hormonal profiles and increasing various seminal parameters such as sperm motility and concentration, as it inhibits aromatization affecting the feedback mechanism to the hypothalamus. This review focuses on our current knowledge of the uses of letrozole for female and male infertility, its mechanisms, and its benefits.
Multidimensional modeling of coronal rain dynamics

We present the first multidimensional, magnetohydrodynamic simulations which capture the initial formation and the long-term sustainment of the enigmatic coronal rain phenomenon. We demonstrate how thermal instability can induce a spectacular display of in-situ forming blob-like condensations which then start their intimate ballet on top of initially linear force-free arcades. Our magnetic arcades host chromospheric, transition region, and coronal plasma. Following coronal rain dynamics for over 80 minutes physical time, we collect enough statistics to quantify blob widths, lengths, velocity distributions, and other characteristics which directly match with modern observational knowledge. Our virtual coronal rain displays the deformation of blobs into V -shaped like features, interactions of blobs due to mostly pressure-mediated levitations, and gives the first views on blobs which evaporate in situ, or get siphoned over the apex of the background arcade. Our simulations pave the way for systematic surveys of coronal rain showers in true multidimensional settings, to connect parametrized heating prescriptions with rain statistics, ultimately allowing to quantify the coronal heating input. Subject headings: magnetohydrodynamics(MHD) — Sun: corona — Sun: filaments, prominences