Advances in Astroparticle Physics and Cosmology (AAPCOS)

12 Oct 2015, 09:00 → 17 Oct 2015, 18:00 Asia/Kolkata

Meghnad Saha Auditorium (Saha Institute of Nuclear Physics)

Astroparticle Physics and Cosmology (APC) Division and Centre for AstroParticle Physics (CAPP) of Saha Institute of Nuclear Physics (SINP), Kolkata will be organising an International workshop on Advances in Astroparticle Physics and Cosmology (AAPCOS) at Saha Institute of Nuclear Physics, Kolkata, India, during 12-17 October, 2015. This conference will focus on the recent excitements in Astroparticle Physics and Cosmology and bring together experimentalists and theorists.

The first two days of the event will be devoted exclusively to pedagogical lecture series on Dark Matter (Theory, Experiment and Phenomenology) meant for students and young researchers.

The rest of the conference will focus on the following topics :

Dark Matter and Dark Energy,  Cosmology and Gravity, Physics and Astrophysics of Neutrinos, Supernovae and Compact Objects, Gravitational Waves, High Energy Cosmic Rays and High Energy Gamma Ray Astrophysics.

The program would include plenary talks, invited talks and sessions with contributed talks.

Participation is by INVITATION ONLY.

Registration/Abstract Submission is now CLOSED.

   

Monday, 12 October

09:00 → 09:45 Registration

09:50 → 10:00 Welcome Address by Prof. Ajit Kumar Mohanty, Director, SINP

10:00 → 11:15 Lecture 1: Dark Matter Detection-I

The quest for the mysterious missing mass of the Universe has become one of the big challenges of today's particle physics and cosmology. Astronomical observations show that only 1% of the matter of the Universe is luminous. Moreover there is now convincing evidence that 85% of all gravitationally observable matter in the Universe is of a new exotic kind, different from the "ordinary" matter surrounding us. In a series of three lectures we discuss past, recent and future efforts made world- wide to detect and/or decipher the nature of Dark Matter. In Lecture I we review our present knowledge of the Dark Matter content of the Universe and how experimenters search for it's candidates; In Lecture II we discuss so-called "direct detection" techniques which allow to search for scattering of galactic dark matter particles with detectors in deep-underground laboratories; we discuss the interpretation of experimental results and the challenges posed by different backgrounds; In Lecture III we take a look at the "indirect detection" of the annihilation of dark matter candidates in astrophysical objects, such as our sun or the center of the Milky Way; In addition we will have a look at efforts to produce Dark Matter particles directly at accelerators and we shall close with a look at alternative non- particle searches and future prospects.

Speaker: Prof. Victor Zacek

Lecture_1_2015_Zacek.pdf

11:15 → 11:45 Tea

11:45 → 13:00 Lecture 2: Low background technologies in underground physics-I

Over the past decades, fundamental physics experiments such as dark matter or double beta decay

have required ultra-low background environments. Successful results from these experiments

depend critically on selection of radiologically ultra-pure materials, high suppression of all types

of radioactivity (cosmic rays, gamma rays, neutrons, radon and its progenies). In the presentation,

I will summarize the deep underground laboratories in the world, the basic methods of selection

of ultra-pure materials, shielding of different types of radioactivity as well as the suppression of

radioactivity caused by the presence of radon. Influence of the background on statistical

significance of the obtained results and the progressive detection methods (pixel detectors)

allowing further suppression of the background will be also presented.

Speaker: Prof. Ivan Stekl (Czech Technical University in Prague)

APPCOS_IS_India_2015_1_final.pptx

13:00 → 14:00 Lunch

14:00 → 15:15 Lecture 3: Dark Matter Theory-I

NA

Speaker: Prof. Paolo Gondolo (University of Utah)

Gondolo-AAPCOSlecture.pdf

15:15 → 16:30 Lecture 4: Low background technologies in underground physics-II

Over the past decades, fundamental physics experiments such as dark matter or double beta decay

have required ultra-low background environments. Successful results from these experiments

depend critically on selection of radiologically ultra-pure materials, high suppression of all types

of radioactivity (cosmic rays, gamma rays, neutrons, radon and its progenies). In the presentation,

I will summarize the deep underground laboratories in the world, the basic methods of selection

of ultra-pure materials, shielding of different types of radioactivity as well as the suppression of

radioactivity caused by the presence of radon. Influence of the background on statistical

significance of the obtained results and the progressive detection methods (pixel detectors)

allowing further suppression of the background will be also presented.

Speaker: Prof. Ivan Stekl (Czech Technical University in Prague)

APPCOS_IS_India_2015_1_final.pptx

16:30 → 17:00 Tea

17:00 → 18:15 Lecture 5: Dark Matter Detection-II

The quest for the mysterious missing mass of the Universe has become one of the big challenges of today's particle physics and cosmology. Astronomical observations show that only 1% of the matter of the Universe is luminous. Moreover there is now convincing evidence that 85% of all gravitationally observable matter in the Universe is of a new exotic kind, different from the "ordinary" matter surrounding us. In a series of three lectures we discuss past, recent and future efforts made world- wide to detect and/or decipher the nature of Dark Matter. In Lecture I we review our present knowledge of the Dark Matter content of the Universe and how experimenters search for it's candidates; In Lecture II we discuss so-called "direct detection" techniques which allow to search for scattering of galactic dark matter particles with detectors in deep-underground laboratories; we discuss the interpretation of experimental results and the challenges posed by different backgrounds; In Lecture III we take a look at the "indirect detection" of the annihilation of dark matter candidates in astrophysical objects, such as our sun or the center of the Milky Way; In addition we will have a look at efforts to produce Dark Matter particles directly at accelerators and we shall close with a look at alternative non- particle searches and future prospects.

Speaker: Prof. Viktor Zacek

Lecture_2_2015_Zacek.pdf

Tuesday, 13 October

10:00 → 11:15 Lecture 6: Dark Matter Theory-II

NA

Speaker: Prof. Paolo Gondolo (University of Utah)

Gondolo-AAPCOSlecture.pdf

11:15 → 11:45 Tea

11:45 → 13:00 Lecture 7: Dark Matter Detection-III

The quest for the mysterious missing mass of the Universe has become one of the big challenges of today's particle physics and cosmology. Astronomical observations show that only 1% of the matter of the Universe is luminous. Moreover there is now convincing evidence that 85% of all gravitationally observable matter in the Universe is of a new exotic kind, different from the "ordinary" matter surrounding us. In a series of three lectures we discuss past, recent and future efforts made world- wide to detect and/or decipher the nature of Dark Matter. In Lecture I we review our present knowledge of the Dark Matter content of the Universe and how experimenters search for it's candidates; In Lecture II we discuss so-called "direct detection" techniques which allow to search for scattering of galactic dark matter particles with detectors in deep-underground laboratories; we discuss the interpretation of experimental results and the challenges posed by different backgrounds; In Lecture III we take a look at the "indirect detection" of the annihilation of dark matter candidates in astrophysical objects, such as our sun or the center of the Milky Way; In addition we will have a look at efforts to produce Dark Matter particles directly at accelerators and we shall close with a look at alternative non- particle searches and future prospects.

Speaker: Prof. Viktor Zacek

Lecture_3_2015_Zacek.pdf

13:00 → 13:05 Closing

13:05 → 14:00 Lunch

14:00 → 18:30 Outreach Programme on Different Aspects of Astroparticle Physics and Cosmology

14:00 Collider to Cosmology- mini bang to the big bang

Collision between two nuclei (mini bang) in an accelerator, such as RHIC, LHC at ultra-relativistic energies melts the hadrons (neutron, proton and mesons) and a new state of matter, consisting of quarks and gluons, Quark Gluon Plasma (QGP) is produced. In the universe, the big bang leads to the creation of the universe. Microsecond after the big bang the universe consisted of quarks, gluons and leptons, somewhat similar to what we are experimenting in the laboratory. What do we learn from these extraordinary events?

Speaker: Prof. Bikash Sinha (VECC, Kolkata)

Dr.Sinha.ppt

14:30 Neutrinos in Astrophysics and Cosmology

NA

Speaker: Prof. Palash Baran Pal (SINP, Kolkata)

15:15 Search for Dark Matter in the sky

NA

Speaker: Prof. Aldo Morselli (INFN)

Morselli_Kolcata_students_rr.pdf

16:00 Tea

16:15 ASTROSAT and beyond: Some science and technology prospects

NA

Speaker: Prof. Biswajit Paul (RRI, Bangalore)

BPAUL_SINP_2015a.pptx

17:00 Dark Energy of the Universe

It has been conclusively proved, from various observations and specifically by studying type 1a supernovae, that we live in an accelerating Universe. All the galaxies are receding from one another, not with the deceleration predicted by General Theory of Relativity as per Einstein's original formulation, but with acceleration. Dark Energy is the presumed source of this acceleration and is known at present to constitute nearly 73% of the energy budget of the Universe. An introductory and semi-popular account will be given of the discovery, present status and implication of this entire phenomenon.

Speaker: Prof. Probir Roy (CAPSS, Bose Institute, Kolkata)

Dark_Energy_of_the_universe_Probir_Roy.pdf

17:45 Square Kilometre Array: Exploring the Universe with the world's largest radio telescope

NA

Speaker: Prof. Tirthankar Roy Choudhury (NCRA-TIFR, Pune)

trc_sinp.pdf

Wednesday, 14 October

09:00 → 09:30 Registration

09:30 → 09:50 Inauguration

09:50 → 10:35 Trends in Dark Matter Physics

NA

Speaker: Prof. Paolo Gondolo (University of Utah)

Gondolo-AAPCOS.pdf

10:35 → 11:20 Supernova Remnants: The Cosmic-ray Accelerators in the Milky Way

Based on the X5 and gamma-ray observations made in the last 30 years, supernova remnants (SNRs) and their strong shock waves, have been widely accepted as the production sites for cosmic rays (CRs) with energies up to 1015 eV. Theoretical models and observations indicate that the diffusive shock acceleration process can produce particles of the required energies and imply that magnetic fields are amplified in very strong collisionless shocks. In SNRs interacting with molecular clouds (MCs), the hadronic model, where a neutral pion produced by the interactions of two protons, decays into two gammas, is the dominating scenario. In young SNRs displaying bright non-thermal X-ray emission, the gamma-ray emission is consistent with the hadronic scenario as well as the leptonic scenario involving the relativistic electrons. In this talk, we would like to discuss about these scenarios of gamma-ray production for 3C 391 and G349.7+0.2, middle-aged mixed-morphology SNRs interacting with MCs, and for Cassiopeia A, a young shell-like SNR, in a multiwavelength frame.

Speaker: Prof. Tülün Ergin (TUBITAK UZAY)

SNRsAsCRAccelerators_TErgin_14Oct2015.pdf

11:20 → 11:50 Tea

11:50 → 12:35 Cosmology in the Post Planck era

The widely heralded, remarkable, progress in cosmology leading to the emergence of a 'standard cosmological model’ has relied on certain key assumptions at different levels. I describe work along multiple facets, largely, from the research program of my group at IUCAA over the past 15 years, that have all attempted to adopt an agnostic approach in drawing cosmological inference independent of such assumptions, in the context of the increasing exquisite observations of the Cosmic Microwave Background CMB anisotropy.

Speaker: Prof. Tarun Souradeep (IUCAA, Pune)

12:35 → 13:00 Dark Energy: An Observational Perspective

Dark energy is one of the most tantalizing mysteries in current cosmological research. A host of observations confirm that about two-thirds of the energy content of the universe comprises this negative-pressure ``dark energy'' component that causes the expansion of the universe to accelerate. Though various theoretical models have been suggested for dark energy, the final conclusion on the nature of dark energy may well come from the observations. In this talk I shall outline the recent developments in observations which are expected to constrain dark energy parameters. I will also outline the potential future directions in dark energy observations.

Speaker: Prof. Ujjaini Alam (ISI, Kolkata)

ujjaini_AAPCOS151014.pdf

13:00 → 14:00 Lunch

14:00 → 14:45 How well can gravitational wave observations of coalescing binaries involving neutron stars constrain the neutron star equation of state?

The Advanced LIGO detectors began observation runs a few weeks ago. This has afforded relativists and astronomers the opportunity to use gravitational waves to improve our understanding of a variety of astronomical objects and phenomena. In this talk I will examine how well gravitational wave observations of coalescing binaries involving neutron stars might constrain the neutron star (NS) equation of state. These astrophysical constraints can improve our understanding of nuclear interactions in ways that complement the knowledge acquired from terrestrial labs. I will study the effects of different NS equations of states in both NS-NS and NS-Black Hole systems, with and without spin, on these constraints.

Speaker: Prof. Sukanta Bose (IUCAA, Pune)

Bose_BNS_AAPCOS_20151015_Submitted.pdf

14:45 → 15:30 Neutrino Oscillation: past, present and future

NA

Speaker: Prof. Srubabati Goswami (Physical Research Laboratory)

aapcos_final_srubabati_goswami.pdf

15:30 → 15:45 Tea

15:45 → 16:10 Supermassive Black Holes and their Host Dark Matter Halos

Through a plethora of observational results we now know that there is a supermassive black hole (SMBH) at the center of every galaxy in the Universe with a fraction of them harboring an active accretion disc and are known as active galactic nuclei (AGN). Thus in the paradigm of structure formation we like to address the question of relating SMBH with their host dark matter halos. Observationally by studying the spatial clustering of SMBH or AGN we can infer about their dark matter hosts. AGN clustering can be characterized within a powerful theoretical framework known as the Halo Occupation Distribution (HOD). In this talk ,I shall discuss about the HOD modeling of AGN using a fully cosmological simulation and show that the underlying theoretical model fits the two-point correlation function (2PCF) of different types of AGN. This provides us an evolutionary picture of AGN along with dark matter halos over cosmic time. In the later half of the talk I shall provide some limitations of the 2PCF fitting method and provide alternative ways to measure the HOD of AGN while trying to address some fundamental questions in AGN physics from a cosmological point-of-view.

Speaker: Prof. Suchetana Chatterjee (Presidency University)

SINP_AAPCOS2015 suchetana.pptx

16:10 → 16:35 Non-directional and directional detection of dark matter in universal bound states

We study the signatures for internal structure of dark matter in direct detection directional and non-directional experiments in the context of asymmetric self-interacting dark matter. The self-interaction cross section of two dark matter particles at low energies is assumed to come close to saturating the S-wave unitarity bound, which requires the presence of a resonance near their scattering threshold. The universality of S-wave near-threshold resonances then implies that the low-energy scattering properties of a two-body bound state of dark matter particles are completely determined by its binding energy, irrespective of the underlying microphysics. The form factor for elastic scattering of the bound state from a nucleus and the possibility of breakup of the bound state produce new signatures in the nuclear recoil energy spectrum. Observations of these recoil structures will give a smoking gun signature of dark matter bound states.

Speaker: Dr Ranjan Laha (Stanford University)

AAPCOS_2015_Direct_detection_Laha.pdf

16:35 → 17:00 Cosmology : Understanding Early and Late Universe

NA

Speaker: Prof. B. C. Paul (NBU, Siliguri)

BCP.pdf

17:00 → 17:25 Hints for a TeV scale $W_R$ at the LHC and constraints on leptogenesis

The discovery of a right-handed charged gauge boson $W_R^\pm$ with mass of around a few TeV, for example through a signal of two leptons and two jets that has been reported by CMS to have a 2.8$\sigma$ local excess or through a signal of a resonance decaying into a pair of Standard Model gauge bosons showing a local excess of 3.4$\sigma$ (2.5$\sigma$ global) reported by ATLAS search, can have severe implications for the leptogenesis mechanism, which offers a very attractive possibility to explain the baryon asymmetry of the universe. In this talk I shall discuss the constraints on the high scale as well as the TeV scale leptogenesis from lepton number violating scattering processes mediated via right-handed heavy neutrinos ($N_{R}$) and the right-handed doubly charged Higgs $\Delta^{++}_{R}$ which can rule out the possibility of successful leptogenesis for $W_{R}^{\pm}$ with mass in the TeV range. Complementing the above results, we shall also discuss the low-energy subgroups of superstring motivated $E_{6}$ model which can allow for high-scale leptogenesis, and explain the excess signal at the LHC reported by the CMS experiment from resonant slepton decay.

Speaker: Chandan Hati (PRL, Ahmedabad)

AAPCOS_chandan_hati.pdf

17:25 → 18:35 Parallel

17:25 Gravity mediated Preheating

In this work we propose a mechanism of natural preheating of our universe induced by the inflaton field dependent effective mass term for the gravitational wave. For any single field inflationary model, the inflaton must go through the oscillatory phase after the end of inflation. As has recently been shown, if the gravitational fluctuation has inflaton dependent mass term, there will be a resonant amplification of the amplitude of the gravitational wave during the oscillatory phase of inflaton though parametric resonance. Because of this large enhancement of the amplitude of the gravitational wave, we show that universe can be naturally pre-heated through a minimally coupled matter field with gravity. Therefore, during the pre-heating phase, there is no need to introduce any arbitrary coupling between the matter field and the inflaton .

Speaker: Dr Debaprasad Maity (IIT Guwahati)

SINP-debu.pdf

17:25 Thermodynamical Interpretation of Geometrical Variables Associated with Null Surfaces

The emergent gravity paradigm interprets gravitational field equations as describing the thermodynamic limit of the underlying statistical mechanics of microscopic degrees of freedom of the spacetime. The connection is established by attributing a heat density $Ts$ to the null surfaces where $T$ is the appropriate Davies-Unruh temperature and $s$ is the entropy density. The field equations can be obtained from a thermodynamic variational principle which extremises the total heat density of all null surfaces. The explicit form of $s$ determines the nature of the theory. We explore the consequences of this paradigm for an arbitrary null surface and highlight the thermodynamic significance of various geometrical quantities. In particular, we show that: (a) A conserved current, associated with the time development vector in a natural fashion, has direct thermodynamic interpretation in all Lanczos-Lovelock models of gravity. (b) One can generalize the notion of gravitational momentum, introduced in arXiv 1506.03814 to all Lanczos-Lovelock models of gravity such that the conservation of the total momentum leads to the relevant field equations. (c) The thermodynamic variational principle which leads to the field equations of gravity can also be expressed in terms of the gravitational momentum in all Lanczos-Lovelock models. (d) Three different projections of gravitational momentum related to an arbitrary null surface in the spacetime lead to three different equations, all of which have thermodynamic interpretation. The first one reduces to a Navier-Stokes equation for the transverse drift velocity. The second can be written as a thermodynamic identity $TdS = dE + P dV$. The third describes the time evolution of the null surface in terms of suitably defined surface and bulk degrees of freedom. The implications are discussed.

Speaker: Mr Sumanta Chakraborty (IUCAA)

Sumanta_Null_Thermodynamics.pdf

17:50 Bounds on IDM from the electroweak vacuum metastability

We add a $Z_2\mbox{-}odd$ complex scalar doublet to the Standard Model at TeV scale. The lightest neutral particle of the doublet is a viable dark matter candidate. We have shown various phase diagrams and point out the regions of absolute stability, meta-stability and instability for the electroweak vacuum and review the bounds on the model.

Speaker: Najimuddin Khan (Indian Institute of Technology Indore)

Najim.pdf

17:50 Inflationary predictions and moduli masses

A generic feature of string/supergravity theories are moduli fields. The implication of moduli fields is a non-standard post-inflationary cosmological time-line when the energy density is dominated by cold moduli particles. This modification in the evolutionary hierarchy implies the preferred range in the number of e-folds between the horizon exit of relevant mode in CMB and the end of inflation is a function of moduli masses. As a result the CMB observables become sensitive to moduli masses. In this work we studied this sensitivity for some representative models of inflation using PLANCK 2015 data and found the results to be highly relevant in confronting models with observations

Speaker: Kumar Das (Saha Institute Of Nuclear Physics)

Inflationary predictions and moduli masses_Kumar Das.pdf

18:05 Consequences of Pilgrim Dark Energy in $f(T, T_G)$ cosmology

Pilgrim dark energy (PDE) model is studied in this paper and Hubble horizon has been used as an IR cutoff. The basic assumption of this model is that phantom acceleration prevents the formation of the BH. The said PDE is considered in a modified gravity $f(T, T_G)$, which has been constructed by Kofinas and Saridakis (2014) on the basis of $T$ (old quadratic torsion scalar) and $T_G$ (new quartic torsion scalar $T_G$ that is the teleparallel equivalent of the Gauss-Bonnet term). We have compiled our work in two phases: Firstly, we have assumed different scale factors such as $a(t)=a_0 t^m$, $H=H_0+\frac{H_1}{t}$, $a(t)=exp(At^m)$ and $a(t)=a_0+\alpha(t-t_0)^{2n}$. We have reconstructed $f$ and subsequently $w_{DE}$ in this scenario. Secondly, we have assumed analytic function such $f=b_0+b_1~t+b_2~t^2+b_3~t^3$ and reconstructed Hubble parameter and $w_{DE}$ without any choice of scale factor. Throughout the study, we have considered $s=-2$ and $s=2$, separately. We have observed that $s=-2$, as described in PDE (Wei, 2012), seems more realistic choice for $s$ than $s=2$ and this outcome of the present reconstruction work is consistent with Wei (2012). Moreover, it has been observed that the reconstructed $w_{DE}$, irrespective of choices of scale factor or a choice of $f$, exhibit a more aggressive phantom-like behavior for $s=-2$ than $s=2$. This result also matches the study of Wei (2012). Hence, it is finally concluded that PDE, when considered in $f(T,T_G)$ gravity is capable of attaining the phantom phase of the universe.

Speaker: Dr Surajit Chattopadhyay (PCMT, Kolkata)

AAPCOS_presentation_Surajit.pdf

18:05 EVIDENCE FOR HIGH DENSITY EARLY UNIVERSE FROM ELEMENTARY PARTICLE PHYSICAL DATA

As supported by the hoop conjecture we show that elementary particles can transform in to micro black holes when its mass density reaches a critical value. These critical values are found to be proportional to the limiting relativistic mass of these particles given by the expression M=hc/2Gm where m is their rest mass. The mass densities of elementary particle black holes is found to mimic the density of the early universe as predicted by cosmological models from 10-43 to 10-20 seconds from the Big Bang. Photon black holes are shown to be identical to the Planck particles which has the highest mass density in the Universe. Our results suggest that elementary particle observations can be used as a probe to the early universe .

Speaker: Prof. Girish T.E (Department of Physics ,UniversityCollege.Trivandrum 695034 India)

Kolkota final.pptx

18:20 The Space-time of Dark-matter

Dark-matter is a hypothetical matter which can't be seen but around 27% of our universe is made of it. Its distribution, evolution from early stage of our universe to present stage, its particle constituents all these are great unsolved mysteries of modern Cosmology and Astrophysics. In this talk I will introduce a special kind of space-time which is known as Bertrand Space-time (BST). I will show this space-time interestingly shows some dark-matter properties like- flat velocity curve, density profile of Dark-matter, total mass of Dark matter-halo, gravitational lensing etc, for that reason we consider BST is seeded by Dark-matter or it is a space-time of Dark-matter. At last I will show using modified gravity formalism the behaviour of the equation of state parameter of Dark-matter and the behaviour of the Newton’s gravitational constant in the vicinity of the singularity.

Speaker: Dipanjan Dey (IIT Kanpur)

Dipanjan Dey,IITK.pdf

Thursday, 15 October

09:00 → 09:45 A geometric approach to moduli stabilization in a higher curvature braneworld

Higher curvature theories are subject of considerable interest in the study of gravitational theories beyond Einstein’s gravity. Braneworld models in presence of higher curvature bulk lead to many interesting features starting from inflationary cosmology to collider phenomenology due to the presence of moduli fields. In this context, stabilization of the moduli in different higher dimensional models is a must for a proper resolution to the gauge hierarchy problem in elementary particle Physics. Such stabilization is normally achieved by introducing an external bulk field (known as stabilizing field) with ad hoc bulk and boundary potential. In this work we demonstrate that such a stabilization can be achieved by a purely geometrodynamical way originating from the higher curvature quantum corrections in the gravity sector.

Speaker: Prof. Soumitra Sengupta (IACS, Kolkata)

aapcos_sinp_soumitra_sengupta.pdf

09:45 → 10:30 If There is Heaven on Earth

We talk about some situations where less frequently discussed dark matter scenarios can substantially affect collider search strategies for new physics.

Speaker: Prof. Biswarup Mukhopadhyaya (HRI, Allahabad)

10:30 → 10:55 Probing the Universe with Cosmic Neutral Hydrogen

As is well known, hydrogen is the most abundant element in the Universe. Hydrogen in the low density intergalactic medium is photoionized by radiation from galaxies and other sources, while they remain in neutral form in very high density regions because of shielding. The evolution of neutral hydrogen through cosmic times passes through a number of interesting phases, namely, the dark ages, cosmic dawn, reionization and post-reionization epoch. Understanding each of these phases holds clue about the cosmology and galaxy formation in our Universe. In the talk, we will review our understanding of the physical processes related to cosmological distribution of neutral hydrogen and then present our recent results on these issues.

Speaker: Prof. Tirthankar Roy Choudhury (NCRA-TIFR, Pune)

trc_aapcos.pdf

10:55 → 11:10 Tea

11:10 → 11:55 Indirect dark-matter searches with gamma-rays experiments : status and future plans from KeV to TeV

Detection of gamma rays and cosmic rays from the annihilation or decay of dark matter particles is a promising method for identifying dark matter, understanding its intrinsic properties, and mapping its distribution in the universe. I will review recent results from the Fermi Gamma-ray Space Telescope and other space-based experiments, and highlight the constraints these currently place on particle dark matter models. I will also discuss the prospects for indirect searches to robustly identify or exclude a dark matter signal using upcoming experiments at energies below Fermi (ASTROGAM ) and above Fermi, Magic and H.E.S.S. (CTA, LHAASO).

Speaker: Prof. Aldo Morselli (INFN)

Morselli_Kolcata_rr.pdf

11:55 → 12:40 Many facets of neutron stars: Astrosat and beyond

We will discuss several interesting aspects of neutron stars that we have pursued over the years along with some very recent results. These include accretion torque, orbital evolution of binary X-ray stars and orbital glitches, quasi-periodic oscillations, self absorption in X-ray pulsars, cyclotron lines in X-ray pulsars, thermonuclear X-ray bursts and their reprocessing etc. We will also discuss some of the important aspects of neutron stars that will be probed in greater detail with ASTROSAT and an X-ray polarimeter and potential use of X-ray pulsars for deep space navigation.

Speaker: Prof. Biswajit Paul (RRI, Bangalore)

BPAUL_SINP_2015b.pptx

12:40 → 13:05 Neutron Star Research in the SKA-Era

SKA, acronym for the Square Kilometer Array, is going to be the largest Radio Telescope ever conceived. As of 5th October 2015 India has become a full member amongst the countries which would be participating in building this telescope and hence would have the primary data rights. Neutron Star science happens to be one of the priorities of this telescope and would revolutionise the research in this area. This talk would focus on a few typical problems which would majorly benefit from the huge volume of data which would also be of very high quality.

Speaker: Prof. Sushan Konar (NCRA-TIFR, Pune)

sushan_aapcos.pdf

13:05 → 14:00 Lunch

14:00 → 14:25 Very High Energy Gamma Ray Astronomy from Hanle

Over a past decade very high energy (VHE) gamma ray astronomy has emerged as a major astronomical discipline. In India, we have a long tradition of experiments in this field. Few years ago, multi-institutional Himalayan Gamma Ray Observatory (HiGRO) collaboration was formed to set up VHE gamma rays experiments at Hanle, a high altitude location in Himalayas. HAGAR, the first phase of this collaboration is operational since 2008. HAGAR has successfully detected VHE gamma ray emission from some of the extragalactic objects like Mrk 421, Mrk 501 as well as galactic sources including Crab nebula/pulsar. Details of HAGAR telescope system and results obtained will be discussed. HiGRO is now gearing up for the next phase, i.e. 21 m diamter MACE telescope, which is being installed at Hanle at present. Details of MACE telescope system and future plans will be discussed.

Speaker: Prof. Varsha R. Chitnis (TIFR, Mumbai)

vrc_aapcos_2015.pdf

14:30 → 18:30 Pijush turns 60

14:30 Introduction

14:40 The Quantum and the Continuum : Einstein's Dichotomous Legacies

This talk begins with a summary of some of Einstein’s seminal contributions in the quantum domain, like Brownian motion and the Light Quantum Hypothesis, as well as on the spacetime continuum enshrined in the theories of special and general relativity. Following up on Einstein’s rationale for postulating the Light Quantum Hypothesis, we attempt to point to a possible dichotomy in his thinking about these two legacies of his, which may have been noticed by him, but was not much discussed by him in the public domain. One may speculate that this may have had something to do with his well-known distaste for the probability interpretation of quantum mechanics as a fundamental interpretation. We argue that Einstein’s general relativity theory itself contains the seeds of a dramatic modification of our ideas of the Einsteinian spacetime continuum, thus underlining the dichotomy even more strongly. We then survey one modern
attempt to resolve the dichotomy, at least partly, by bringing into the spacetime continuum, aspects of quantum mechanics with its underlying statistical interpretation, an approach which Einstein may not have whole-heartedly endorsed, but which seems to work so far, with good prospects for the future.

Speaker: Prof. Parthasarathi Majumdar (RKMVU, Belur)

PijushFEST15.pdf

15:10 NA

NA

Speaker: Prof. Naba K. Mondal (TIFR, Mumbai)

15:40 Detecting Supernova Neutrinos by Iron and Lead Detectors

Supernova neutrinos can excite the nuclei of different detector materials beyond their neutron emission thresholds through the charged current and neutral current interactions. The emitted neutrons, if detected, can be a signal for the supernova event. In this talk we shall discuss some results for the lead and iron detectors using the realistic neutrino fluxes and energies given by Basel/Darmstadt simulations for a 18 solar mass progenitor supernova.

Speaker: Prof. Kamales Kar (RKMVU, Belur)

oct15kk.pdf

16:10 Tea

16:30 Reminiscence Talks

18:00 Talk

Speaker: Prof. Pijushpani Bhattacharjee (SINP, Kolkata)

19:00 → 22:30 Conference Dinner

Friday, 16 October

09:00 → 09:45 Direct Dark Matter Searches: Threshold detectors and new techniques

This talk summarizes recent activities in the sector of dark matter searches with superheated liquids, and gives an overview of proposed new initiatives for directional searches and new techniques to explore the low mass frontier in the GeV and sub-GeV dark sector.

Speaker: Prof. Viktor Zacek (Université de Montreal)

AAPCOS_2015_Zacek_final.pdf

09:45 → 10:30 Searching for Baryons

The current precision cosmological measurements, in agreement with big bang nucleosynthesis studies, tell us that approximately 95 percent of the Universe is 'dark' and only 5 percent of the Universe is 'visible' which comprises of baryons. However, observations reveal only a small fraction of this baryon budget. A key cosmological question arises as to 'where are these missing baryons?'. Simulations and past observations suggest that some of these are in the diffuse cosmic web. Recently, they have been observed, and speculated, to be hiding in the outskirts of massive halos, from Milky Way type galaxies to clusters. Upcoming surveys have the potential to unravel the mystery of the missing baryons.

Speaker: Prof. Subhabrata Majumdar (TIFR, Mumbai)

10:30 → 10:55 Some theoretical aspects of magnetars

Compact stars with strong magnetic fields (magnetars) have been observationally determined to have surface magnetic fields of order of 10^14 –10^15 G, the implied internal field strength being several orders larger. We discuss the effect of strong field on the dense matter expected to be inside neutron stars and so called quark stars and hybrid stars. We also discuss its effect on some observational effect which depend the nature and composition of matter inside neutron stars.

Speaker: Prof. Monika Sinha (Indian Institute of Technology Jodhpur)

AAPCOS_monika.pptx

10:55 → 11:10 Tea

11:10 → 11:55 Thermonuclear flame propagation on neutron stars

Accreted matter accumulated on a low magnetic field neutron star intermittently burns via thermonuclear runaway processes, and gives rise to bursts observed in X-rays. During the rise of the X-ray intensity, the thermonuclear flame spreads to engulf the entire stellar surface. Such flame propagation in extreme environment, which is relevant for several branches of physics, is an interesting field in its own right, and is important to probe the super-dense degenerate matter at stellar cores. I will discuss the theoretical and observational aspects of flame spreading, its importance, and why ASTROSAT will be very useful to advance our knowledge.

Speaker: Prof. Sudip Bhattacharyya (TIFR, Mumbai)

bhattacharyya_SINP_2015.pdf

11:55 → 12:40 Double Beta Decay

Experimental searches for neutrino-less double beta decay ($0 \nu \beta \beta$) are one of the most active research topics in neutrino physics. The observation of such process is in fact of major importance since it will prove the Majorana nature of neutrinos and may give access to their absolute mass scale. The Majorana nature of the neutrino would have interesting implication in many extensions of the Standard Model of particle physics. On the other hand, two neutrino double beta decay ($2 \nu \beta \beta$) provides needed information for further development of nuclear theory (nuclear matrix elements). During the talk, the subjects of $0 \nu \beta \beta$ and $2 \nu \beta \beta$ decays, the most important experiments in the field and the obtained results will be introduced.

Speaker: Prof. Ivan Stekl (Czech Technical University in Prague)

APPCOS_IS_India_2015_1_v4.pptx

12:40 → 13:05 Role of backreaction in an accelerating universe

It is apparent from several observations that the present universe is undergoing an era of accelerated expansion. On the other hand, the observable universe exhibits inhomogeneities at various scales. The backreaction from inhomogeneities may affect the background metric in a non-trivial way. Here we explore a consequence of such backreaction which may possibly alter the future evolution of the presently accelerating universe, leading to avoidance of the big-rip.

Speaker: Prof. Archan S. Majumdar (SNBNCBS, Kolkata)

archan_aapcos15.ppt

13:05 → 14:00 Lunch

14:00 → 14:45 The Highest Energy Neutrinos: Status and Questions

NA

Speaker: Prof. Raj Gandhi (HRI, Allahabad)

Gandhi_AAPCOS_Oct15.pdf

14:45 → 15:30 The Cherenkov Telescope Array (CTA)

The Cherenkov Telescope Array (CTA) is a next generation observatory for ground-based gamma-ray astronomy to be built in the near future by an international consortium. The plan is to build 2 arrays one in the southern and the other in the northern hemisphere with hundreds of Imaging Atmospheric Cherenkov Telescopes of assorted size. This will enable to achieve an order of magnitude improvement in the sensitivity and angular resolution and also span a wide energy range of 10 GeV to 10TeV. The CTA will serve as an open observatory to a wide astrophysics community and will provide a deep insight into the non-thermal high-energy universe. It will have a large discovery potential in key areas of astronomy, astrophysics and fundamental physics research which include the study of the origin of cosmic rays and their role in the Universe, the nature and variety of particle acceleration around black holes, and the inquiry into the ultimate nature of matter and physics beyond the Standard Model, searching for dark matter and effects of quantum gravity. In this talk I shall describe the CTA project and its current status.

Speaker: Prof. B. S. Acharya (TIFR, Mumbai)

BSA-CTA-AAPCOS-2015.pptx

15:30 → 15:45 Tea

15:45 → 16:30 How does the Higgs potential survive inflation ?

After the discovery of the 125 GeV mass Higgs, it was shown that the value of the Higgs quartic coupling becomes negative on renormalization at high energies. The energy scale at which the Higgs potential becomes unstable is 10^(11) GeV. During inflation quantum fluctuations will drive the vev of the Higgs field to $< \phi^2 > ~ H^2, where H the expansion rate of the scale factor at the time of inflation is expected to be 10^{14} GeV. Therefore during inflation the Higgs field will roll down to large negative values. This inconsistency between Higgs potential and inflation even when the Higgs field is not the inflation is an open problem. I will discuss ways on which this problem has been solved by introducing new physics beyond the standard model. I will also discuss one idea where the solution to the Higgs instability problem is provided by the Hawking-Gibbons temperature of the de-Sitter space during inflation.

Speaker: Prof. Subhendra Mohanty (Physical Research Laboratory)

Higgs-Instability-Inflation_subhendra_mohanty.pdf

16:30 → 16:55 7 keV sterile neutrino dark matter in U(1)_R-lepton number model

I shall discuss about keV sterile neutrino dark matter in a supersymmetric model with U(1)_R symmetry in the light of a recent observation of an X-ray line signal at around 3.5 keV, detected in the X-ray spectra of Andromeda galaxy and various galaxy clusters including the Perseus galaxy cluster. In this model the U(1)_R symmetry is identified with lepton number. The model provides a small tree level mass to one of the active neutrinos and also renders a suitable warm dark matter candidate in the form of a sterile neutrino. Light neutrino masses and mixing can be explained once one-loop radiative corrections are taken into account. The scalar sector of this model can accommodate a Higgs boson with a mass of ~ 125 GeV. In this model gravitino is the lightest supersymmetric particle and we also discuss the cosmological implications of this light gravitino with a mass of order GeV.

Speaker: Prof. Sourov Roy (IACS, Kolkata)

sinp-aapcos-2015-talk_sourov_roy.pdf

16:55 → 17:20 Direct Dark Matter Searches and future prospects

NA

Speaker: Prof. Venktesh Singh (BHU, Varanasi)

VSINGH-SINP-2015.ppt

17:20 → 18:55 Parallel

17:20 Entropy Functional and Second Law in Curvature Squared Gravity

Nonrenormalizability of Einstein gravity has made us to believe that it is a low energy effective theory of a more fundamental theory, for example string theory. This low energy effective action generally contains an infinite number of higher curvature terms apart from the lowest order Einstein Hilbert term. It is thus important to survey the effects of such higher curvature terms on known features of General Relativity like thermodynamics of Black Holes (BH). This work addresses issues related to entropy of BH in higher curvature theories.

Speaker: Dr Srijit Bhattacharjee (IIT Gandhinagar)

Talk_AAPCOS_srijit.pdf

17:20 Two neutrino double electron capture measurement using pixel detectors

The TGV collaboration has been investigating the applicability of pixel detectors in the detection of two neutrino double electron capture (2$\nu$EC/EC) in $^{106}$Cd. Pixel detector gives spatial information along with energy of the particle, thus helps to identify and remove the background signals. The collaboration has proposed a Silicon Pixel Telescope (SPT) for the next generation experiment; where a pair of Si pixel detectors with enriched Cd foil in the middle forms the detection unit. Prototype units of SPTs (using 0.5 and 1 mm Si sensors) were recently fabricated and installed in the LSM underground laboratory, France. A detailed account of the SPT setup and preliminary results from background measurements will be presented.

Speaker: Dr Joshy M. jose (Czech Technical University in Prague)

AAPCOS_Kolkata_2015_joshy.pdf

17:40 Impact of sterile neutrinos on CP measurements at DUNE

Long-baseline neutrino experiments aim to measure the parameters responsible for neutrino oscillations. Now that θ13 has been conclusively shown to be non-zero and not too small, the focus has shifted to the measurement of the (Dirac) CP phase δCP that determines whether or not oscillating neutrinos violate CP. one of the main aim of the upcoming long baseline experiment DUNE is to measure this phase. But, there are evidences suggesting the possibility of the existence of one (or possibly more) more generation of neutrino (called sterile neutrino) which may have small mixings with the standard model neutrinos. These extra generation of neutrino brings in extra CP phases into play. The additional phases due to the presence of even one sterile neutrino of mass ∼ 1 eV can potentially create a significant degeneracy in measuring δCP at DUNE. On the basis of our recent paper arXiv:1508.06275, I will talk about the large magnitude of these effects using probability level analysis and neutrino-antineutrino asymmetry calculations and will also discuss about how it translates into significant event rate deviations at DUNE.

Speaker: Mehedi Masud (HRI)

masud_slides.pdf

17:45 HIgher spins as saviour of Quantum Universe

We consider toy example of 3 dimensional universe defined via definite thermal properties. This is modelled by Eucledian Einstein gravity with positive cosmological constant. In this background we couple higher spin interactions with pure gravity and calculate Euclidean path integral perturbatively. We confine ourselves to the static patch of the 3 dimensional de Sitter space. This geometry, when Euclideanlized is equivalent to 3-sphere. However, infinite number of topological quotients of this space by discrete subgroups of the isometry group are valid Euclidean saddles as well. Pure Einstein gravity is known to diverge, when all saddles are included as contribution to the thermal partition functions (also interpreted as the Hartle Hawking state of in the cosmological scenario). We show how higher spins, described by metric-Fronsdal fields help making the partition function finite. Curiously, the convergence is not achieved by mere inclusion of spin-3, but requires spin-4 interactions. This explains thermal stability of the quantum universe in presence of higher spins, albeit in a toy model

Speaker: Dr Rudranil Basu (Indian Institute of Science Education and Research, Pune)

aapcos_rudranil_basu.pdf

17:55 The Direct Detection of Boosted Dark Matter at High Energies and PeV events at IceCube

We study the possibility of detecting dark matter directly via a small but energetic component that is allowed within present-day constraints. Drawing closely upon the fact that neutral current neutrino nucleon interactions are indistinguishable from DM-nucleon interactions at low energies, we extend this feature to high energies for a small, non-thermal but highly energetic population of DM particle \chi created via the decay of a significantly more massive and long-lived non-thermal relic \phi which forms the bulk of DM. If \chi interacts with nucleons, its cross-section, like the neutrino-nucleus coherent cross-section, can rise sharply with energy leading to deep inelastic scattering, similar to neutral current neutrino-nucleon interactions at high energies. Thus, its direct detection may be possible via cascades in very large neutrino detectors. As a specific example, we apply this notion to the recently reported three ultra-high energy PeV cascade events clustered around 1-2 PeV at IceCube. We discuss the features which may help discriminate this scenario from one in which only astrophysical neutrinos constitute the event sample in detectors like IC.

Speaker: Aritra Gupta (HRI, Allahabad)

TalkSinp_ARITRA.pdf

18:10 Exploring Octant and CP violation at DUNE in presence of Reactor Experiments

Deep Underground Neutrino Experiment (DUNE) is an upcoming long baseline experiment at Fermilab, which aims to answer many fundamental questions both in particle physics and astrophysics. Neutrino physics is in the precision era. DUNE can answer questions regarding neutrino mass ordering, the octant of atmospheric mixing angle $\theta_{23}$ and most importantly it can probe CP violation in the neutrino sector. Here in this work, we have explored the octant and CP violation sensitivity at DUNE by combining data from reactor experiments. With a 35 kt Liquid Argon time-projection chamber deployed as a far detector, at Sanford Underground Research Facility, DUNE is capable of resolving the octant ambiguity as well as discovering CP violation in the neutrino sector. Our work shows that combining reactor data with DUNE improves both octant and CP violation sensitivity significantly.

Speaker: Debajyoti Dutta (HRI, Allahabad)

AAPCOS-debajyoti.pdf

18:10 The k-essence scalar field in the context of Supernova Ia observations

A k-essence scalar field model having (non canonical) Lagrangian of the form L=-V(\phi)F(X) where X=1/2g^{\mu\nu}\nabla_{\mu}\phi\nabla_{\nu}\phi with constant V(\phi) is shown to be consistent with luminosity distance-redshift data observed for type Ia Supernova. For constant V(\phi), F(X) satisfies a scaling relation which is used to set up a differential equation involving the Hubble parameter H, the scale factor a and the k-essence field \phi. H and a are extracted from SNe Ia data and using the differential equation the time dependence of the field \phi is found to be: \phi(t) \sim \lambda_0 + \lambda_1 t + \lambda_2 t^2. The constants \lambda_i have been determined. The time dependence is similar to that of the quintessence scalar field (having canonical kinetic energy) responsible for homogeneous inflation. Furthermore, the scaling relation and the obtained time dependence of the field \phi is used to determine the X-dependence of the function F(X).

Speaker: Arka Moulik (RKMVU, Belur)

AAPCOS2015_arka_moulik.pdf

18:25 Exploring Non Standard Physics in Long-Baseline Neutrino Oscillation Experiments

After the recent discovery of large th_{13}, the focus has been shifted to address the remaining fundamental issues like neutrino mass ordering and CP-violation in leptonic sector. Future proposed Long-Baseline facilities like DUNE (1300 km baseline from FNAL to Homestake) and LBNO (2290 km baseline from CERN to Pyhasalmi) are well suited to address these issues at high confidence level. Not only to the standard framework, these experiments are highly capable to look for some new physics beyond the Standard Model scenario. In this work, we explore whether these high precision future facilities are sensitives to new U(1) global symmetries and upto which confidence level.

Speaker: Sabya Sachi Chatterjee (Institute of Physics, Bhubaneswar)

AAPCOS_sabya_sachi.pdf

Saturday, 17 October

09:00 → 09:45 LZ: A 2nd Generation Dark Matter Direct Search Experiment

The LZ collaboration has proposed a 2nd generation direct dark matter search experiment, which builds on the experience gained with the LUX and ZEPLIN series of experiments on the two-phase xenon TPC technique. It features an active target volume of ~7 tonnes and a robust 3-layer shield system consisting of a xenon skin volume and a liquid scintillator veto, embedded in the existing 6m diameter water tank at the 4850' level of the Sanford Underground Research Facility. We have developed a novel design for the liquefaction, recirculation and purification for this unprecedented large volume of xenon. Our studies of backgrounds are comprehensive and predict a fiducial volume larger than 5 tonnes, in which the dominant electron and nuclear recoil backgrounds are from astrophysical neutrinos. The projected sensitivity for a 1,000 day running period for the WIMP-nucleon cross section is below 2.5x10^-48 cm^2 at a WIMP mass of 50 GeV. We will present some details of the advanced design of LZ, the background model, and our physics goals.

Speaker: Prof. Mani Tripathi (UC Davis)

Tripathi_LUX_LZ_AAPCOS.pdf

09:45 → 10:30 Cosmic Accelerators with H.E.S.S.

The High Energy Stereoscopic System (H.E.S.S.) has provided a view of the Galactic Plane as well as the extra-Galactic sky in the southern hemisphere with unprecedented sensitivity. It has revealed powerful particle accelerators via their TeV emission within and outside the Galaxy showing their spatial, spectral and temporal characteristics. This helps us understand the physics of the individual sources as well as their environment. The studies of active galactic nuclei (AGN) in particular enable us to do TeV cosmology probing the extra-Galactic background light (EBL), as well as Lorentz Invariance violating effects. The addition of the new 28 m^2 telescope enables observations down to lower energies (< 100 GeV) and with better energy resolution. This allows to push further on all the aforementioned fronts. In this talk, I will highlight some of the more recent exciting results from H.E.S.S. on the Galactic Center, the Large Magellanic Clouds as well as the Active Galactic Nuclei and their implications on astroparticle physics in general.

Speaker: Dr Nachiketa Chakraborty (Max-Planck-Institut fuer Kernphysik)

10:30 → 10:55 General relativistic viscous accretion disc and generation of bipolar jets

We revisit the general relativistic viscous accretion disc. As in Newtonian fluid, the viscous tensor is proportional to the shear tensor in relativistic fluid too, and the constant of proportionality is the constant of viscosity. However, in relativity the shear tensor is much more complicated, containing four accelerations, gradient of three velocities, expansion of world line terms etc. This inherent complication makes a consistant study of viscous accretion discs around black holes very difficult. In this presentation, we solve the equations of general relativistic viscous disc in steady state. We show that such accreting flows may admit shock waves. The extra heating term in the post-shock disc may spew out bipolar jets. In order to determine the jet streamline and jet cross section we obtained the corresponding von Zeipel cylinders. We then trace the matter that will escape through these surfaces. We also show that 4 to 5 % of accreting matter escapes as bipolar relativistic jets. Comparison with Newtonian plus pseudo-Newtonian and the pure general relativistic studies shows that the jets are much stronger in the latter case. And finally we discuss the observational implications.

Speaker: Prof. Indranil Chattopadhyay (ARIES, Nainital)

Indra_AAPCOS15.ppt

10:55 → 11:10 Tea

11:10 → 11:35 Nucleosynthesis in neutron star crust

NA

Speaker: Prof. Sarmistha Banik (BITS Pilani, Hyderabad)

Nucleosynthesis in NSs crust matter for SINP_sarmistha_banik.pptx

11:35 → 11:55 Nonthermal Two Component Dark Matter Model for Fermi-LAT $\gamma$-ray excess and 3.55 keV X-ray Line

A two component model of nonthermal dark matter is formulated to simultaneously explain the Fermi-LAT results indicating a $\gamma$-ray excess observed from our Galactic Centre in the 1-3 GeV energy range and the detection of an X-ray line at 3.55 keV from extragalactic sources. Two additional Standard Model singlet scalar fields $S_2$ and $S_3$ are introduced. These fields couple among themselves and with the Standard Model Higgs doublet $H$. The interaction terms among the scalar fields, namely $H$, $S_2$ and $S_3$, are constrained by the application of a discrete $\mathbb{Z}_2\times \mathbb{Z}^\prime_2$ symmetry which breaks softly to a remnant $\mathbb{Z}^{\prime \prime}_2$ symmetry. This residual discrete symmetry is then spontaneously broken through an MeV order vacuum expectation value $u$ of the singlet scalar field $S_3$. The resultant physical scalar spectrum has the Standard Model like Higgs as $\chi_{{}_{{}_1}}$ with $M_{\chi_{{}_{{}_1}}}\sim 125$ GeV, a moderately heavy scalar $\chi_{{}_{{}_2}}$ with $50 \,\,{\rm GeV} \leq M_{\chi_{{}_{{}_2}}}\leq 80\,\,{\rm GeV}$ and a light $\chi_{{}_{{}_3}}$ with $M_{\chi_{{}_{{}_3}}} \sim 7$ keV. There is only tiny mixing between $\chi_{{}_{{}_1}}$ and $\chi_{{}_{{}_2}}$ as well as between $\chi_{{}_{{}_1}}$ and $\chi_{{}_{{}_3}}$. The lack of importance of domain wall formation in the present scenario from the spontaneous breaking of the discrete symmetry ${\mathbb{Z}_2^{\prime\prime}}$, provided $u\leq 10$ MeV, is pointed out. We find that our proposed two component dark matter model is able to explain successfully both the above mentioned phenomena $-$ the Fermi-LAT observed $\gamma$-ray excess (from the $\chi_{{}_{{}_2}} \rightarrow {\rm b} \bar{\rm b}$ decay mode) and the observation of the X-ray line (from the decay channel $\chi_{{}_{{}_3}}\rightarrow\gamma \gamma$) by the XMM-Newton observatory.

Speaker: Anirban Biswas (HRI, Allahabad)

aapcos-2015_anirban_biswas.pdf

11:55 → 12:40 To Lambda or not to Lambda?

NA

Speaker: Prof. Supratik Pal (ISI, Kolkata)

supratik_aapcos15.pdf

12:40 → 13:00 Concluding Session

13:00 → 14:00 Lunch & Closing