178,533 research outputs found
R -Axion at Colliders
No full textWe study the effective theory of a generic class of hidden sectors where supersymmetry is broken together with an approximate R-symmetry at low energy. The light spectrum contains the gravitino and the pseudo-Nambu-Goldstone boson of the R-symmetry, the R-axion. We derive new model-independent constraints on the R-axion decay constant for R-axion masses ranging from GeV to TeV, which are of relevance for hadron colliders, lepton colliders, and B factories. The current bounds allow for the exciting possibility that the first sign of supersymmetry will be the R-axion. We point out its most distinctive signals, providing a new experimental handle on the properties of the hidden sector and a solid motivation for searches of axionlike particles
Red Clump stars in the Boötes III stellar system
No full textWe report on the detection of a population of Red Clump (RC) stars probably associated with the recently discovered stellar system Boötes III. The RC is identified as a 3σ peak in the luminosity function (LF) of colour-selected stars extracted from the Sloan Digital Sky Survey data base. The peak is consistently detected in the g,r,i and z LFs at the expected luminosity of a typical RC at the distance of Boötes III. Moreover, the stars around the LF peak show a maximum of surface density nearly coincident with the reported centre of the system. Assuming that the detected feature is the genuine RC of Boötes III, we find that the system has the horizontal branch morphology typical of old and metal-poor dwarf spheroidals, it has an integrated magnitude MV ~= -5.8 +/- 0.5 and an ellipticity ɛ ~ 0.5, quite typical of the recently identified new class of very faint dwarf galaxies
On the orbital stability for a class of nonautonomous NLS
No full textFollowing the original approach introduced by T. Cazenave and P.L. Lions in [4] we prove the existence and the orbital stability of standing waves for the
following class of NLS:
(0.1)
i@tu + u − V (x)u + Q(x)u|u|p−2 = 0, (t, x) 2 R × Rn, 2 < p < 2 + 4/n
and
(0.2) i@tu − Δ2u − V (x)u + Q(x)u|u|p−2 = 0, (t, x) 2 R × Rn, 2 < p < 2 + 8/n
under suitable assumptions on the potentials V (x) and Q(x).
More precisely we assume V (x),Q(x) 2 L∞(Rn) and meas{Q(x) < λ0} ε (0,∞) for a suitable λ0<0. The main point is the analysis of the compactness of minimiziang sequences to suitable constrained minimization problems related to (0.1) and (0.2)
The mass function of Omega Centauri down to 0.15 Msolar
No full textBy means of deep FORS1/VLT and ACS/Hubble Space Telescope observations of a wide area in the stellar system ? Cen we measured the luminosity function of main-sequence stars down to R = 22.6 and IF814W = 24.5. The luminosity functions obtained have been converted into mass functions and compared with analytical initial mass functions (IMFs) available in the literature. The mass function obtained, reaching M ~ 0.15Msolar, can be well reproduced by a broken power law with indices ? = -2.3 for M > 0.5Msolar and ? = -0.8 for M < 0.5Msolar. Since the stellar populations of ? Cen have been proved to be actually unaffected by dynamical evolution processes, the mass function measured in this stellar system should represent the best approximation of the IMF of a star cluster. The comparison with the MF measured in other Galactic globular clusters suggests that possible primordial differences in the slope of the low-mass end of their MF could exist
Maximizers for Gagliardo–Nirenberg inequalities and related non-local problems.
No full textIn this paper we study the existence of maximizers for two families of interpolation inequalities, namely a generalized Gagliardo–Nirenberg inequality and a new inequality involving the Riesz energy. Two basic tools in our argument are a generalization of Lieb’s Translation Lemma and a Riesz energy version of the Brézis–Lieb lemma
Ground states for semi-relativiscti SPS energy
No full textWe prove the existence of ground states for the semi-relativistic Schrodinger-Poisson-Slater energy
I-alpha,I- beta(rho) = inf (u is an element of H 1/2 (R3) integral R3 vertical bar u vertical bar 2dx=rho) 1/2 parallel to u parallel to(2)(H1/2(R3)) + alpha integral integral(R3xR3) vertical bar u(x)vertical bar(2)vertical bar u(y)vertical bar(2)/vertical bar x - y vertical bar dxdy - beta integral(R3) vertical bar u vertical bar(8/3)dx alpha, beta > 0 and rho > 0 is small enough. The minimization problem is L-2 critical and in order to characterize the values alpha, beta > 0 such that I-alpha,I- beta(rho) > -infinity for every rho > 0, we prove a new lower bound on the Coulomb energy involving the kinetic energy and the exchange energy. We prove the existence of a constant S > 0 such that
1/S parallel to phi parallel to(L8/3(R3))/parallel to phi parallel to(1/2)(H1/2(R3)) <= (integral integral(R3 x R3) vertical bar phi(x)vertical bar(2)vertical bar phi(y)vertical bar(2)/vertical bar x - y vertical bar dxdy)(1/8)
for all phi is an element of C-0(infinity)(R-3). Besides, we show that similar compactness property fails if we replace the inhomogeneous Sobolev norm parallel to u parallel to(2)(H1/2(R3)) by the homogeneous one parallel to u parallel to(H1/2(R3)) in the energy above
Discovery of a stellar system in the background of 47 Tucanae. A new cluster of the Small Magellanic Cloud?
No full textWe report on the discovery of a stellar system in the background of the Galactic globular cluster 47 Tucanae (NGC 104), located 14.8 arcmin North-West of the cluster center. The object, whose apparent diameter is D≃ 30 arcsec, is partially resolved into stars on the available CCD images, reaching a limiting magnitude of V~ 22.5, and is detected as a significant (more than 5 sigma) overdensity of blue stars (B-V<0.7). The color magnitude diagram of the system, its characteristic projected size and its position in the sky suggest that it is an intermediate-old age cluster belonging to the Small Magellanic Cloud, whose outskirts lie in the background of 47 Tuc. Although less likely, the possibility that the object is an unknown dwarf galaxy in the outskirts of the Local Group cannot completely be ruled out by the present data
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