SINP/TNP/2010/01
Submitted on :6-1-2010
| Author(s) : | Raktim Abir and Munshi G. Mustafa |
| Title : | Universality in fluidity |
| Abstract : | Based on fluid dynamics and mode-mode-coupling theory the hot fluids despite various microscopic degrees of freedom exhibit a remarkable universality with a new fluidity measure in hydrodynamic as well as in nonhydrodynamic region. We also show that this result is independent of the choice of the fluid dynamics, {\em viz.}, relativistic or nonrelativistic. Being a hot relativistic fluid QGP should follow the same universality constrained by both the viscous and the thermal flow modes in it. |
| Archive entry : | arXiv:1001.0692[hep-ph] |
SINP/TNP/2010/02
Submitted on :4-3-2010
| Author(s) : | Kumar S. Gupta, E. Harikumar, Siddhartha Sen and M. Sivakumar |
| Title : | The Central Charge of the Warped $AdS^3$ Black Hole |
| Abstract : | The AdS/CFT conjecture offers the possibility of a quantum description for a black hole in terms of a CFT. This has led to the study of general $AdS^3$ type black holes with a view to constructing an explicit toy quantum black hole model. Such a CFT description would be characterized by its central charge and the dimensions of its primary fields. Recently the expression for the central charges $(C_L, C_R)$ of the CFT dual to the warped $AdS^3$ have been determined using asymptotic symmetry arguments. The central charges depend, as expected, on the warping factor. We show that topological arguments, used by Witten to constrain central charges for the BTZ black hole, can be generalized to deal with the warped $AdS^3$ case. Topology constrains the warped factor to be rational numbers while quasinormal modes are conjectured to give the dimensions of primary fields. We find that in the limit when warping is large or when it takes special rational values the system tends to Witten's conjectured unique CFT's with central charges that are multiples of 24. |
| Archive entry : | arXiv:.[hep-th] |
SINP/TNP/2010/03
Submitted on :5-3-2010
| Author(s) : | Gautam Bhattacharyya, Tirtha Sankar Ray |
| Title : | A phenomenological study of 5d supersymmetry |
| Abstract : | Supersymmetry and extra dimension need not be mutually exclusive options of physics for the TeV scale and beyond. In this paper, we envisage a phenomenological scenario by embedding the 4d constrained minimal supersymmetric standard model in a flat 5d $S_1 /Z_2$ orbifold, with the inverse radius of compactification at the TeV scale. The gauge, Higgs and the third generation matter multiplets are placed in the bulk. From a 4d perspective, the bulk has $N=2$ supersymmetry which entails a special non-renormalization theorem giving rise to a significant numerical impact on the renormalization group running of various parameters. The brane supersymmetry corresponds to $N=1$ which we assume to be broken in an unspecified but phenomenologically acceptable way. Given this set-up, we study how the gauge and Yukawa couplings and the $N=1$ brane supersymmetry breaking soft masses run through the energy scale exciting the Kaluza-Klein states at regular interval. We present our results by showing the allowed/disallowed zone in the plane of the common scalar mass ($m_0$) and common gaugino mass ($M_{1/2}$). Our plots are the first 5d versions of the often displayed 4d $m_0$--$M_{1/2}$ plots, and we provide reasons behind the differences between the 4d and 5d plots. |
| Archive entry : | arXiv:1003.1276[hep-ph] |
SINP/TNP/2010/04
Submitted on :26-4-2010
| Author(s) : | Pritibhajan Byakti, Palash B Pal |
| Title : | Theta-parity in supersymmetry |
| Abstract : | We consider invariance of the action of N=1 supersymmetric theories under the change of sign of the fermionic co-ordinate in superspace. We show that the R-parity can be realized as a special implementation of this symmetry. Other implementations in the supersymmetric extension of the standard model can be related to lepton number and baryon number parities. |
| Archive entry : | arXiv:1004.4055[hep-ph] |
SINP/TNP/2010/05
Submitted on :14-7-2010
| Author(s) : | Najmul Haque and Munshi G. Mustafa |
| Title : | Quark Number Susceptibility in Hard Thermal Loop Perturbation Theory |
| Abstract : | We formulate a thermodynamically consistent Hard Thermal Loop perturbation theory at the first derivative level of the thermodynamic potential by employing an external probe to the system. Using this we obtain various thermodynamic quantities in leading order, and also, in particular, the quark number susceptibility as a response to such an external disturbance. The results so obtained are separated in soft and hard momenta naturally and are also in agreement with those obtained in the two-loop approximately self-consistent $\Phi$-derivable Hard Thermal Loop resummation. Further, we also calculate the quark number susceptibility, which is related to the correlation function through the thermodynamic sum rule associated with the symmetry of the system. Within the Hard Thermal Loop approximation this connection was not shown earlier and also the equivalence of the quark number susceptibility in two ways. |
| Archive entry : | arXiv:1007.2076[hep-ph] |
| Other information : | 20 pages, 4 figures |
SINP/TNP/2010/06
Submitted on :23-8-2010
| Author(s) : | R. Yaresko, Munshi G. Mustafa, and B. Kampfer |
| Title : | Relativistic Expansion of Electron-Positron-Photon Plasma Droplets and Photon Emission |
| Abstract : | The expansion dynamics of hot electron-positron-photon plasma droplets is dealt with within relativistic hydrodynamics. Such droplets, envisaged to be created in future experiments by irradiating thin foils with counter-propagating ultra-intense laser beams, are sources of flashes of gamma radiation. Warm electron-positron plasma droplets may be identified and characterized by a broadened 511 keV line. |
| Archive entry : | arXiv:1008.3495[physics] |
SINP/TNP/2010/07
Submitted on :29-9-2010
| Author(s) : | Palash B. Pal |
| Title : | Dirac, Majorana and Weyl fermions |
| Abstract : | This is a pedagogical article which discusses various kinds of fermion fields: Dirac, Majorana and Weyl. The definitions and motivations for introducing each kind of fields is discussed, along with the connections between them. It is pointed out that these definitions have to do with the proper Lorentz group, and not with respect to any discrete symmetry. The action of discrete symmetries like charge conjugation and CP on various types of fermion fields, particularly important for Majorana fermions, has also been clarified. |
| Archive entry : | arXiv:1006.1718[hep-ph] |
SINP/TNP/2010/08
Submitted on :12-10-2010
| Author(s) : | Carsten Greiner, Najmul Haque, Munshi G. Mustafa, Markus H. Thoma |
| Title : | Low Mass Dilepton Rate from the Deconfined Phase |
| Abstract : | We discuss low mass dilepton rates ($\le 1$ GeV) from the deconfined phase of QCD using both perturbative and non-perturbative models and compare with those from lattice gauge theory and in-medium hadron gas. Our analysis suggests that the rate at very low invariant mass ($ M\le 200$ MeV) using the nonperturbative gluon condensate in a semiempirical way within the Green function dominates over the Born-rate and independent of any uncertainty associated with the choice of the strong coupling in perturbation theory. On the other hand the rate from $\rho-q$ interaction in the deconfined phase is important between 200 MeV $\le M \le 1 GeV as it is almost of same order of the Born-rate as well as in-medium hadron gas rate. Also the higher order perturbative rate, leaving aside its various uncertainties, from HTL approximation becomes reliable at $M\ge 200$ MeV and also becomes comparable with the Born-rate and the lattice-rate for $M\ge 500$ MeV, constraining on the broad resonance structures in the dilepton rate at large invariant mass. We also discuss the lattice constraints on the low mass dilepton rate. Furthermore, we discuss a more realistic way to advocate the quark-hadron duality hypothesis based on the dilepton rates from QGP and hadron gas than it is done in the literature. |
| Archive entry : | arXiv:1010.2169[hep-ph] |
SINP/TNP/2010/09
Submitted on :28-10-2010
| Author(s) : | Baishali Chakraborty, Kumar S. Gupta and Siddhartha Sen |
| Title : | Effect of topology on the critical charge in graphene |
| Abstract : | We show that the critical charge for the Dirac excitations in gapless graphene depends on the spatial topology of the sample. In particular, for graphene cones, the effective value of the critical charge can tend towards zero for a suitable angle of the conical sample. We discuss the nature of the scattering phase shifts, quasi-bound state energies and local density of states for a gapless graphene cone and determine the dependence of these physical quantities on the sample topology. |
| Archive entry : | arXiv:1010.[cond-mat] |
SINP/TNP/2010/10
Submitted on :22-11-2010
| Author(s) : | Asmaa Abada, Gautam Bhattacharyya, Debottam Das, Cedric Weiland |
| Title : | A possible connection between neutrino mass generation and the lightness of a NMSSM pseudoscalar |
| Abstract : | One of the interesting properties of the NMSSM is that it can accommodate a light pseudoscalar of order 10 GeV. However, such scenarios are challenged by several experimental constraints, especially those related to the fermionic decays of the pseudoscalar. In this paper, we extend the NMSSM field content by two gauge singlets, with lepton numbers $+1$ and $-1$. This serves the twin purpose of generating neutrino masses via the inverse see-saw mechanism and keeping the option of a very light pseudoscalar experimentally viable by opening dominant invisible decay channels of the pseudoscalar which help it evade the existing bounds. |
SINP/TNP/2010/11
Submitted on :23-11-2010
| Author(s) : | Raktim Abir, Carsten Greiner, Mauricio Martinez, Munshi G. Mustafa |
| Title : | Generalisation of Gunion-Bertsch Formula for Soft Gluon Emission |
| Abstract : | We generalise the most extensively used Gunion-Bertsch formula for the soft gluon emission in a perturbative QCD, which could be very important for the phenomenology of the hot and dense matter produced in the heavy-ion collisions. |
| Archive entry : | arXiv:1011.4638[nucl-th] |
SINP/TNP/2010/12
Submitted on :27-11-2010
| Author(s) : | Gautam Bhattacharyya, Philipp Leser, Heinrich P\ |
| Title : | Exotic Higgs boson decay modes as a harbinger of $S_3$ flavor symmetry |
| Abstract : | Discrete symmetries employed to explain flavor mixing and mass hierarchies can be associated with an enlarged scalar sector which might lead to exotic Higgs decay modes. In this paper, we explore such a possibility in a scenario with $S_3$ flavor symmetry which requires three scalar $SU(2)$ doublets. The spectrum is fixed by minimizing the scalar potential, and we observe that the symmetry of the model leads to tantalizing Higgs decay modes potentially observable at the CERN Large Hadron Collider (LHC). |
| Archive entry : | arXiv:1006.5597[hep-ph] |
SINP/TNP/2010/13
Submitted on :29-12-2010
| Author(s) : | Pritibhajan Byakti |
| Title : | Discrete R-symmetries and F-term Supersymmetry Breaking |
| Abstract : | We have shown that in a large number of generic and renormalizable Wess-Zumino models existence of a $Z_n$ R-symmetry is sufficient to break supersymmetry spontaneously. This implies that existence of a $Z_n$ R-symmetry is a necessary condition for supersymmetry breaking in generic and renormalizable Wess-Zumino models. |
| Archive entry : | arXiv:1008.2578[hep-ph] |