123633440
Oblique electroweak parameters S and T for superconformal field theories
55061398
LHC string phenomenology
We argue that it is possible to address the deeper LHC inverse problem, to gain insight into the underlying theory from LHC signatures of new physics. We propose a technique which may allow us to distinguish among, and favor or disfavor, various classes of underlying theoretical constructions using (assumed) new physics signals at the LHC. We think that this can be done with limited data (5–10 fb−1), and improved with more data. This is because of two reasons: (a) it is possible in many cases to reliably go from (semi)realistic microscopic string constructions to the space of experimental observables, say, LHC signatures, and (b) the patterns of signatures at the LHC are sensitive to the structure of the underlying theoretical constructions. We illustrate our approach by analyzing two promising classes of string compactifications along with six other string-motivated constructions. Even though these constructions are not complete, they illustrate the point we want to emphasize. We think that using this technique effectively over time can eventually help us to meaningfully connect experimental data to microscopic theory.
118571038
Unravelling strings at the CERN LHC
We construct LHC signature footprints for four semirealistic string/M theory vacua with a minimal supersymmetric standard model visible sector. We find that they all give rise to limited regions in LHC signature space and are qualitatively different from each other for understandable reasons. We also propose a technique in which correlations of LHC signatures can be effectively used to distinguish among these string theory vacua. We expect the technique to be useful for more general string vacua. We argue that further systematic analysis with this approach will allow LHC data to disfavor or exclude major 'corners' of string/M theory and favor others. The technique can be used with limited integrated luminosity and improved.
119200117
The Higgs as a probe of supersymmetric extra sectors
A bstractWe present a general method for calculating the leading contributions to h0 → gg and h0 → γγ in models where the Higgs weakly mixes with a nearly supersymmetric extra sector. Such mixing terms can play an important role in raising the Higgs mass relative to the value expected in the MSSM. Our method applies even when the extra sector is strongly coupled, and moreover does not require a microscopic Lagrangian description. Using constraints from holomorphy we fix the leading parametric form of the contributions to these Higgs processes, including the Higgs mixing angle dependence, up to an overall coefficient. Moreover, when the Higgs is the sole source of mass for a superconformal sector, we show that even this coefficient is often calculable. For appropriate mixing angles, the contribution of the extra states to h0 → gg and h0 → γγ can vanish. We also discuss how current experimental limits already lead to non-trivial constraints on such models. Finally, we provide examples of extra sectors which satisfy the requirements necessary to use the holomorphic approximation.
53143827
OPE methods for the holomorphic Higgs portal
A bstractWe develop a systematic and general approach to study the effective Higgs Lagrangian in a supersymmetric framework in which the Higgs fields in the visible sector couple weakly to another sector. The extra sector may be strongly coupled in general. It is assumed to be superconformal in the ultraviolet, but develop a mass-gap with supersymmetry breaking in the infrared. The main technique used in our approach is that of the operator product expansion (OPE). By using OPE methods we are able to compute the parameters in the Higgs Lagrangian to quadratic order and make general statements that are applicable to many classes of models. Not only does this approach allow us to understand the traditional problems plaguing simple models from a different perspective, it also reveals new possibilities for solutions of these problems. The methods and results of our work should be useful in constructing a viable and natural model of physics beyond the Standard Model.
119028722
Origins of hidden sector dark matter I: cosmology
We present a systematic cosmological study of a universe in which the visible sector is coupled, albeit very weakly, to a hidden sector comprised of its own set of particles and interactions. Assuming that dark matter (DM) resides in the hidden sector and is charged under a stabilizing symmetry shared by both sectors, we determine all possible origins of weak-scale DM allowed within this broad framework. We show that DM can arise only through a handful of mechanisms, lending particular focus to Freeze-Out and Decay and Freeze-In, as well as their variations involving late time re-annihilations of DM and DM particle anti-particle asymmetries. Much like standard Freeze-Out, where the abundance of DM depends only on the annihilation cross-section of the DM particle, these mechanisms depend only on a very small subset of physical parameters, many of which may be measured directly at the LHC. In particular, we show that each DM production mechanism is associated with a distinctive window in lifetimes and cross-sections for particles which may be produced in the near future. We evaluate prospects for employing the LHC to definitively reconstruct the origin of DM in a companion paper.
53709333
Supernovae-induced accretion and star formation in the inner kiloparsec of a gaseous disc
We consider the effects of supernovae (SNe) on accretion and star formation in a massive gaseous disc in a large primeval galaxy. The gaseous disc we envisage, roughly 1 kpc in size with ≳108 M⊙ of gas, could have formed as a result of galaxy mergers where tidal interactions removed angular momentum from gas at larger radius and thereby concentrated it within the central ∼1 kpc region. We find that SNe lead to accretion in the disc at a rate of roughly 0.1–1 M⊙ yr−1 and induce star formation at a rate of ∼10–100 M⊙ per year which contributes to the formation of a bulge; a part of the stellar velocity dispersion is due to SN shell speed from which stars are formed and a part due to the repeated action of stochastic gravitational field of SNe remnant network on stars. The rate of SN in the inner kpc is shown to be self-regulating, and it cycles through phases of low and high activity. The SN-assisted accretion transports gas from about 1 kpc to within a few pc of the centre. If this accretion were to continue down to the central black hole then the resulting ratio of black hole mass to the stellar mass in the bulge would be of the order of ∼ 10−2–10−3, in line with the observed Magorrian relation.
118728848
On Geodesic Flows and Their Deformations in Bertrand Space-times
We study the energy conditions and geodesic deformations in Bertrand space-times. We show that these can be thought of as interesting physical space-times in certain regions of the underlying parameter space, where the weak and strong energy conditions hold. We further compute the ESR parameters and analyze them numerically. The focusing of radial time-like and radial null geodesics is shown explicitly, which verifies the Raychaudhuri equation.
118788230
GEODESIC FLOWS AND THEIR DEFORMATIONS IN BERTRAND SPACETIMES
In this article we will discuss some features of a particular spacetime called Bertrand space-time of Type II (BST-II). The talk discusses about the energy conditions and the ESR parameters in this spacetime.
17597500
Differential Rotation Enhanced Dissipation of Tides in the PSR J0045–7319 Binary
Recent observations of PSR J0045-7319, a radio pulsar in a close eccentric orbit with a massive B star companion, indicate that the system's orbital period is decreasing on a timescale of ≈ 5 × 105 yr. This is much shorter than the timescale of ≈ 109 yr given by the standard theory of tidal dissipation in radiative stars. Observations also suggest that the B star is rotating rapidly, perhaps at nearly its breakup speed. We show that the dissipation of the dynamical tide in a star rotating in the same direction as the orbital motion of its companion (prograde rotation) with a speed greater than the orbital angular speed of the star at periastron (supersynchronous rotation) results in an increase in the orbital period of the binary system with time. Thus, if the magnitude of the rotation speed of the B star is supersynchronous, then the observed decrease in the orbital period requires the direction of the rotation of the B star to be retrograde. For subsynchronous prograde rotation of the B star, the energy in the dynamical tide, even if it is dissipated in one orbital period, is too small to account for the observed orbital evolution, unless the rotation speed is close to zero. Slow rotation of the B star is, however, ruled out by the observed apsidal motion of the system (Lai et al., Kaspi et al.). Thus, in order to explain both the observed apsidal motion and the orbital evolution of the PSR J0045-7319 binary, the B star must have retrograde rotation. If the rotation in the interior of the B star is not synchronized, which we show is the case, then the work of Goldreich & Nicholson suggests that the B star should be rotating differentially, with the rotation speed of the outer layers close to the synchronous value. We show that the dissipation of the dynamical tide in such a differentially rotating B star is enhanced by almost 3 orders of magnitude, leading to an orbital evolution time for the PSR J0045-7319 binary that is consistent with the observations.
18521155
H I observations of two molecular clouds with extremely large velocity dispersions
We have mapped two molecular clouds at (i, b) = (3.2°, + 0.3°) and (i, b) = (5.4°, - OS) in 21-cm line and continuum emission. These clouds show unusually large velocity dispersions of more than 100 km s -1 (FWHM) which has also been seen in 12CO, 13CO and CS emissions. This dispersion is approximately an order of magnitude larger compared with giant molecular clouds. From our H I observations we estimate that the atomic mass of the cloud at i = 3.2° is about 1.5 x 105 Mo and the mass of the cloud at i = 5.4° is 7 x 104 Mo. The ratio of total molecular mass to atomic mass for these clouds appears to be normal for clouds near the Galactic Centre. The main peculiar feature of these clouds is their abnormally large velocity dispersion; the extent in velocity is from about 0 [local standard of rest (LSR)] to 200 km S-I. These clouds are connected, in the i-v plane, to high-velocity ridges that extend over several degrees of longitude. These properties, we believe, provide important clues to the physical process responsible for their large velocity dispersion.