HIGH ENERGY PHYSICS THEORY GROUP
"THE CRITICAL MASS HAS BEEN REACHED"
Seminar
Room 201, Physics 1 Building, Dept of Physics, Chulalongkorn U.
Thanaporn Sichanugrist
January 31, 2024, 1:30 pm
Title: Wave-like Dark Matter Detection using Qubits
Abstract:
Various quantum sensors including qubits, commonly employed in quantum computers, exhibit ideal properties for dark matter detection. Coherent wave-like dark matter can excite qubits, leading to detectable signals; we discuss the case of using transmon qubits in dark matter detection in [Phys.Rev.Lett. 131 (2023) 21, 211001]. In addition, through the appropriate quantum circuit, we demonstrate that the signal rate can be enhanced to scale quadratically, rather than linearly, with the number of sensor qubits [arXiv: 2311.10413]. In this talk, I will delve into the theoretical framework underlying qubit excitation induced by dark matter, elucidate the signal-enhancement mechanism with the specific quantum circuit, and briefly introduce the ongoing experiments at the UTokyo (ICEPP)
On Site: Room 201, Physics 1 Building, Chulalongkorn University
https://chula.zoom.us/j/97521913995?pwd=UUVxV01LYUQrbDFuZC9NaUo4UEVHZz09
Meeting ID: 975 2191 3995
Password: 716710
Piyabut Burikham
October 21, 2022, 2 pm
Title: Massive neutron star with holographic multiquark(MQ) core and MQ star from Sakai-Sugimoto model
Abstract: Extreme density compresses baryons together so tightly that baryons overlap, quarks from each baryon start to roam freely to neighbouring baryons. As a result, the radius of confinement grows bigger. Coupling between quarks could still be strong and the quarks inside could form multiquark(MQ) bound states with the screened potential. Holographic Sakai-Sugimoto(SS) model provides a top-down approach to address the physical properties of the MQ states, and its thermodynamic stability. It is found that the MQ phase is the most thermodynamically preferred phase under extreme density above the nuclear saturation density n0 = 0.16 fm^-3 and moderate temperature below trillion Kelvins. Such conditions are found inside the neutron star. We study various physical properties of such NS with MQ core, as well as the pure MQ star.
On Site: Room 201, Physics 1 Building, Chulalongkorn University
zoom:
https://chula.zoom.us/j/98477840801?pwd=OFFTUE41MzdNaHpFU0xjU1ZraGdkUT09
Meeting ID: 984 7784 0801
Password: 179318
BYON NUGRAHA JAYAWIGUNA
October 14, 2022, 2 pm
Title: Ultracompact Object in the nonlocal gravity
Abstract: Gravitational wave is the most useful tool nowadays to detect compact objects and black holes. In a theoretical way, we can study this aspect by invoking gravitational perturbation theory resulting Regge-Wheeler equation (axial) that describes three useful points: Effective potential, Quasinormal mode, and the Gravitational wave. In this talk, I will review these concepts and how we can extract an effective potential to obtain the eigenfunction (gravitational wave). Moreover, we will employ nonlocal Tolman VII model to study these aspects and compare them with the well-known literature.
On Site: Room 201, Physics 1 Building, Chulalongkorn University
zoom:
https://chula.zoom.us/j/93297676078?pwd=akJTL2FRd3JjYlI0WERSaVRQbE5VZz09
Meeting ID: 932 9767 6078
Password: 192239
Peera Pongkitiwanichakul
June 9, 2022, 1 pm
Title: Role of Parallel Solenoidal Electric Field on Energy Conversion
in 2.5D Decaying Turbulence with a Guide Magnetic Field
Abstract:
We perform 2.5D particle-in-cell simulations of decaying turbulence in the presence of a guide (out-of-plane) background magnetic field. The fluctuating magnetic field initially consists of Fourier modes at low wavenumbers (long wavelengths). With time, the electromagnetic energy is converted to plasma kinetic energy (bulk flow +thermal energy) at the rate per unit volume of J· E for current density J and electric field E. Such decaying turbulence is well known to evolve toward a state with strongly intermittent plasma current. Here we decompose the electric field into components that are irrotational, Eir, and solenoidal (divergence-free), Eso. Eir is associated with charge separation, and J · Eir is a rate of energy transfer between ions and electrons with little net change in plasma kinetic energy. Therefore, the net rate of conversion of electromagnetic energy to plasma kinetic energy is strongly dominated by J · Eso, and for a strong guide magnetic field, this mainly involves the component Eso,∥ parallel to the total magnetic field B. We examine various indicators of the spatial distribution of the energy transfer rate J∥ · Eso,∥, which relates to magnetic reconnection, the best of which are (1) the ratio of the out-of-plane electric field to the in-plane magnetic field, (2) the out-of-plane component of the nonideal electric field, and (3) the magnitude of the estimate of current helicity Unified Astronomy Thesaurus concepts: Plasma physics (2089); Solar magnetic reconnection (1504); Interplanetary turbulence (830)
ZOOM link:
Topic: Panda seminar
Time: Jun 9, 2022 01:00 PM Bangkok
Join Zoom Meeting
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Meeting ID: 955 7968 4168
Password: 309515
Muhammad F. Alfian R. Sakti
"Hidden conformal symmetry for
Kerr-Newman-NUT-AdS black holes"
November 30, 2021, 1:30 pm
Room 201, Physics 1 Building, Chulalongkorn University.
Join Zoom Meeting
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Meeting ID: 997 7498 9136
Password: 771553
Abstract:
Following the famous Kerr/CFT correspondence conjecture, we find that the non-extremal Kerr-Newman-NUT-AdS black holes are holographically dual to the hidden 2D CFTs. We explicitly construct two different conformal field theories (known as the $J$ and $Q$ pictures) dual to the black holes, which correspond to the angular momentum $J$, and the electric charge $Q$ of the black holes. Moreover, we show that the two pictures are included in a more general CFT (known as the general picture). We find perfect agreement between the macroscopic Bekenstein-Hawking entropy of the black holes and the microscopic Cardy entropy of CFT. We then compute the absorption cross-section of the scalar probes in the background of the non-extremal Kerr-Newman-NUT-AdS black holes. We find agreement with the microscopic results from CFT.
Tirawut Worrakitpoonpon
"Limitation of symmetry breaking in spherical collapse experiments"
April 2, 2021
In this presentation, we present the theoretical and numerical works of the spherical collapse of self-gravitating systems and their shape evolution. Spherical collapse model is widely employed as a toy model to understand the origin of the elliptical galaxy. In cold systems, that the initial triaxiality seeded by the Poissonian fluctuation is amplified by the collapse has been verified in various collapse simulations. The dependence on the particle number (N) has also been reported. However, the conclusion for the systems with finite velocity dispersion is different: the initial velocity dispersion has a counter-balancing effect to the gravity. We demonstrate that a simple analytical work, based on the Lin-Mestel-Shu instability theory, by estimating the radial profiles of these counter-balancing forces and their corresponding fluctuations lets us obtain the critical N. Below this number, the symmetry breaking is effective, while it is ineffective above that number. We find that the predicted scaling of the critical N agrees well with the numerical simulations at low density gradient. Beyond that limit, the underlying processes are more complicated than those described by the proposed mechanism.
David Senjaya, S.Si.
"Canonical Quantization of Fundamental Black
Hole as Gravitational Atom"
2 pm, March 24, 2021, Room 201 Physics 1 Building, CU.
Gravitational field is usually neglected in calculation of atomic energy levels as its effect is much weaker than the electromagnetic field, but that is not the case for a particle orbiting a black hole. In this work, canonical quantization of a particle under a gravitational field exerted by this tiny but very massive object-which is static, rotating, neutral, charged or their combinations-is carried out. By using this method, very rare exact result of the particle’s quantized energy can be discovered. The presence of a very strong attractive field and the horizon make the energy complex valued and force the corresponding wave function to be a quasi-bound state. Moreover, by taking a non relativistic limit, the system becomes a gravitational atom in sense that hydrogenic atoms energy levels and wave functions can be recovered. Obtaining these exact solutions for fundamental black holes effectively empowers us to deal with more complex black holes such as cosmological black holes or black hole solutions emerging from modified gravity.
Pornpipat Ouppajan
2 pm, February 5, 2021
A demonstration comprising a sheet of elastic fabric attached with arigid frame and a central mass placed on the center of the sheet forthe visualization of a curved spacetime has been investigated. Tostudy whether the demonstration using fabric can replicate planetarymotion, a mathematical description of the shape of the curved fabricand equation of motion of the rolling mass are needed. Firstly, thecalculus of variation was applied to obtain an equation describing theshape of the fabric. Next, the fabric equation as the function of thecentral mass was numerically solved and compared with the shape of thefabric measured from the experiment. Then, the equation of motion ofthe rolling mass on the fabric was derived using the law of energyconservation and momentum conservation. The solution to equation ofmotion for the rolling mass on the curved fabric shows that if theframe and the fabric is very large, the unbounded orbit will not existfrom the demonstration. This is the difference from Newtonian gravityand Schwarzschild spacetime. In addition, there exist only circularorbit and elliptic orbit with or without precession from thedemonstration.
Asst. Prof. Dr. Patipan Uttayarat (Srinakharinwirot University)
วันพุธที่ 18 กันยายน 2019 เวลา 14:30 ห้อง 201 ตึกฟิสิกส์ 1 จุฬา
Title: Phenomenology of the Type-II Seesaw Model
Abstract: In this talk I will give a brief overview of neutrino mass generation mechanism. I will then focus on the Type-II seesaw model which in principal could be probe at colliders. I will discuss how to probe different parts of parameter space using different observables. Finally, I will present the updated viable parameter space of the model.
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Sirachak Panpanich (Chulalongkorn University)
August 28, 2019 เวลา 14:00 ห้อง 201 ตึกฟิสิกส์ 1 จุฬา
Recent low-redshift observations give value of the present-time Hubble parameter H0 = 74 km/sec/Mpc, roughly 10% higher than the predicted value H0 = 67.4 km/sec/Mpc from Planck's observations of the CMB and the LCDM model. Phenomenologically, we show that the Friedmann equation requires an extra unknown component X to contribute a negative density to the Universe in order to resolve the Hubble tension without changing the Planck's constraint on the matter and dark energy densities. For the extra negative density to be sufficiently small, its equation-of-state parameter must satisfy 1/3 <= w_X <= 1. We propose a quintom model of two scalar fields that realizes this condition and successfully resolve the Hubble tension. One scalar field acts as a quintessence while another “phantom” scalar conformally couples to matter in such a way that viable cosmological scenario can be achieved. The model depends only on two parameters, \lambda_{\phi} and \delta which represent rolling tendency of the self-interacting potential of the quintessence and the strength of conformal phantom-matter coupling respectively.
In this talk I will explain what the Hubble tension is and show that how the quintom dark energy model solve this problem.
Nipol Chaemjumrus (Imperial College London)
July 31, 2019 เวลา 13:30 ห้อง 201 ตึกฟิสิกส์ 1 จุฬา
Title: Duality and Geometry of String Theory
Abstract: In this talk, first I will introduce some basic ideas on superstring theories in ten dimensions, namely, type IIA, type IIB, type I, heterotic SO(32), and heterotic E8xE8. Next, I will review duality symmetries, namely, S-duality, T-duality, and U-duality, and how these duality symmetries connect each superstring theory. Lastly, I will talk about the T-duality chain of special holonomy domain wall solutions. This example can arise in string theory in solutions in which these backgrounds appear as fibers over a line. The cases with 3-torus with H-flux over a line were obtained from identifications of suitable NS5-brane solutions, and are dual to D8-brane solutions. This T-duality chain implies that K3 surface should have a limit in which it degenerates to a long neck capped off by suitable smooth geometries.
Takol Tangphati (Chulalongkorn University)
July 19, 2019; 13:30 ห้อง 201 ตึกฟิสิกส์ 1 จุฬา
Title: The Black Hole Perturbations
Abstract: I have studied the perturbation of black holes with scalar and tensor fields. There are three phases of the fields: the early times phase depends on the initial condition; the quasinormal modes phase, where the field exponentially decays; the late time tail phase, where the field decays as a power-law function. In this talk, I will focus on the quasinormal mode (QNMs) and late time tail phases. In order to find the quasinormal frequencies, the perturbation equation is written in frequency domain and solved by the numerical method called Asymptotic Iteration Method (AIM). In this work, my colleagues and I found the pattern of quasinormal frequencies near the horizons of charge black holes where the real part of QNMs is proportional to electromagnetic potential and the real part is of multiple of the surface gravity. However, the quasinormal frequencies are not the only mode generated from the black hole perturbation. The late time tail modes or power law decay modes emerge after the quasinormal mode era. We use the finite difference method to visualize the late time tail modes of scalar and tensor fields perturbing the black hole background metric. The numerical results correspond to the analytic solutions that amplitude of the fields is proportional to t^{-2l+3}.
Dr. Nick Poovuttikul (University of Iceland)
June 5, 2019; 13:30
Title: Higher-form, Higher-group and hydrodynamics
Abstract: Recently, number of works has been emphasising on the role of a rather unconventional global symmetry of quantum field theories, ranging from QCD to SPT phases. I will start by discussing roles of the so-called higher-form global symmetry (associating with line/defect operators) in various QFT. More interestingly, the higher-form symmetry and ordinary global symmetry can be mixed together in a certain way to form a larger structure called higher-group. I will discuss the systems where this higher-group global symmetry appears, in particular when gauging a subgroup of QFT with anomaly.
The main focus of this talk will be about the hydrodynamic description of the higher-form and higher-group global symmetry and their observable consequences.
Asst. Dr. Pittayuth Wongjun
3 May 2019; 14.00
Title: Rotating Black String and Its Thermodynamics
Abstract: One of solutions of Einstein field equation with cylindrical symmetry is known as black string solution. In this presentation, I provide how to obtain the rotating black string solution in dRGT massive gravity called rotating-dRGT black string solution. The horizon structure of the black string is explored. The horizon structures of the black string are explored. The thermodynamical properties of the black string are presented. We found that it is possible to obtain the Hawking-Page phase transition depending on the additional structure of the graviton mass, while it is not possible for rotating-AdS/dS black string. By analyzing the free energy, we also found that the stable rotating black string is bigger than the non-rotating one.
Dr. Yermek Aldabergenov
April 11, 2019; 13:30
ขอประชาสัมพันธ์สัมมนาฟิสิกส์ วันพฤหัสที่ 11 เมษายน 2019 เวลา 13:30 ห้อง 201 ตึกฟิสิกส์ 1 จุฬา
โดย Yermek Aldabergenov (Chulalongkorn University)
Title: Starobinsky model in supergravity
Abstract: Starobinsky model (R+R^2 gravity) is a simple single-field model of inflation that is in a very good agreement with CMB observations. On the other hand since supersymmetry is a very useful tool for constructing Beyond the Standard Model physics, it motivates us to study supersymmetric extensions of inflationary models, in our case - Starobinsky model. In this seminar I will review Starobinsky supergravity and then talk about unified models of (Starobinsky-like) inflation and SUSY breaking.
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Atis Yosprakob
3 April 2019; 13.00
Title: Introduction to Matrix String Theory
Abstract: Superstring theory is proposed to be the ultimate theory that describes gravity and other fundamental interactions. The biggest problem is that the theory is not uniquely defined perturbatively (landscape problem). As a result, many formulations are proposed as its non-perturbative counterpart which can potentially solve this problem. In this talk, we are interested in IKKT matrix model which is conjectured as the non-perturbative theory for type IIB superstring theory. Model constructions as well as interesting results will be discussed.
Dr. Anibal Sierra Garcia
1 March 2019 : 16:00
ขอประชาสัมพันธ์สัมมนาฟิสิกส์ วันศุกร์ที่ 1 มีนาคม 2019 เวลา 16:00 ห้อง 201 ตึกฟิสิกส์ 1 จุฬา
โดย Dr. Anibal Sierra Garcia (Chulalongkorn University)
Title: Phase transitions from AdS to dS in Gauss-Bonnet gravity
Abstract: I will present a bubble nucleation mechanism which changes the asymptotics from Anti de Sitter to de Sitter. The action for gravity is Einstein-Gauss-Bonnet in 5 dimensions and no matter is required. The bubble contains a dS solution in the interior, and an AdS one in the exterior. These two are matched together without matter, which is
forbidden in Einstein-Hilbert gravity. This kind of phase transitions should also appear in generic higher curvature gravities.
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Dr. Spyros Sypsas
30 January 2019 : 13:30
ขอประชาสัมพันธ์สัมมนาฟิสิกส์ วันพุธที่ 30 มกราคม 2019 เวลา 13:30 ห้อง 201 ตึกฟิสิกส์ 1 จุฬา
โดย Dr. Spyros Sypsas (Chulalongkorn University)
Title: Mapping the inflationary landscape with cosmological data
Abstract:
It is natural to expect that during inflation there were more than one degrees of freedom at play, whose dynamics affect the CMB. The cosmological collider program aims at finding patterns in the CMB observables that are "smoking guns" for such additional fields. We will see that in fact, we can reconstruct a whole class of Lagrangians from CMB observations, probing the interactions of light fields during inflation, thus mapping the potential landscape.
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Dr. Chun Hung Chen
26 December 2018
Title: The study of spin-3/2 fields in the spherically symmetric spacetimes
Abstract: Black hole perturbation theory is not a new area for research. People consider various kinds of the field equation perturbative classical spacetimes and present many well-known results, for example, the Regge-Wheeler equation, the Zerilli equation, and the Teukolsky equation. In early 20th, researchers start to generalize these equations into higher dimensional cases, both for Bosonic perturbation and Fermionic perturbation. It is however that the spin-3/2 perturbation in higher dimensional spacetimes is a gap with fewer studies, and this is the topic I am going to present today. In these works, we use analytical methods to study the spin-3/2 fields in higher dimensional spherically symmetric spacetimes, starting with the eigenvalue problem on higher dimensional spheres. With these eigenmodes, we can separate the angular part of spherically symmetric spacetimes and derive the radial equation. In this seminar, I will present some results on the Schwarzschild black hole and Reissner-Nordstrom black hole, and showing the related Quasinormal modes by using semi-analytical methods.
Krai Cheamsawat
19 December 2018
Title: Free energy dependence on spatial geometry for (2+1)-dimensional QFTs
Abstract: We consider (2+1)-QFT at finite temperature on a product of time with a static spatial geometry. The suitably defined difference of thermal vacuum free energy for the QFT on a deformation of flat space is a UV finite quantity, and for reasonable fall-off conditions on the deformation is IR finite too. For perturbations of flat space we show that free energy difference goes quadratically with perturbation amplitude and may be computed from the linear response of the stress tensor. As an illustration we compute it for a holographic CFT finding that at any temperature, and for any perturbation, the free energy decreases. Similar behaviour was previously found for free scalars and fermions obtained from heat kernel method, and for unitary CFTs at zero temperature, suggesting (2+1)-QFT may generally energetically favour a crumpled spatial geometry. In this controlled setting, at small curvature relative to the thermal scale, we can also do the hydrodynamics expansion up to the fourth order. Then the free energy variation is determined by a curvature correction to the stress tensor and indeed it agrees with the numerical result.
Dr. Pree-cha Kiatkirakajorn
30 November 2018
Title: Instabilities in drying colloids: from micro-scale dynamics to structure
Abstract: During drying, colloidal dispersions can show a variety of transformations such as buckling, wrinkling, cracking, delamination, shear banding, structural anisotropy, etc. These phenomena are responses of microscopic interactions, between particles and between the fluid medium. If we understand how these interactions scale up to the macroscopic effect, we then can control or prevent these instabilities to occur during the drying of dispersions. Here, we show the experimental results of drying colloidal films together with a simple model, Poisson-Boltzmann cell model, which aims to predict the osmotic pressure, the collective diffusivity of a charged colloidal dispersion that arise during the drying. This model had no free parameters. We performed drying experiment in Hele-Shaw cell. The SAXS technique was used to measure the changing of volume fraction across the liquid solid transitions of a drying colloidal dispersion. We also explored the effect of microscopic interaction through shear bands and cracks. Eventually, we showed that the structural anisotropy which the liquid-solid drying front left behind could be the pathways of cracks.
Dr. Wiphu Rujopakarn
23 November 2018 Part I
Title: Probing the peak epoch of galaxy assembly with the Very Large Array and Atacama Large Millimeter/submillimeter Array
Abstract: The peak epoch of galaxy assembly, cosmic star formation rate history, and quasar activity, 1 < z < 3, holds the key to our understanding of galaxy evolution. This epoch is also the ``dust era,’’ during which typical star-forming galaxies are nearly obscured to optical observations. Dust obscuration poses challenges to our understanding of some of the most fundamental processes, especially down to galactic scales, where the current frontier questions in galaxy evolution lie: How did galactic spheroids form since z ~ 3? How did galaxies and their supermassive black holes co-evolve? What mechanism drives and halts the intense star formation at the peak of the cosmic star formation rate history? Answering these questions requires a dust-independent, spatially-resolved study of individual galaxies at the peak of their assembly to map their star formation and accretion activities, which is now possible with the Very Large Array (VLA) and Atacama Large Millimeter/submillimeter Array (ALMA). I will present first results from the most sensitive VLA and ALMA surveys of the Hubble Ultra-Deep Field (HUDF) that capture the morphology of star formation and pinpoint the locations of AGN at z ~ 2. Building on the results of this work - which includes the deepest VLA image ever made - I will discuss future prospects for galaxy evolution studies combining the VLA, ALMA, and JWST.
Asst. Prof. Dr. Tirawut Worrakitpoonpon
31 October 2018
Title: The study of finite-N effect in self-gravitating astrophysical process
Abstract: Self-gravitating N-body system is widely employed as toy model to understand the dynamical process of many astrophysical objects such as galaxy or large-scale structure. In such system the finite-N fluctuation is present but the role of this graininess nature has rarely been mentioned in past astrophysical literatures. In statistical mechanics context, the embedded finite-N fluctuation, albeit microscopically, is found non-negligible for the dynamics of many hypothetical N-body systems with long-range interactions. In this seminar, I will present the study of finite-N effect to the astrophysical collapse process governed by self-gravity, which is a member of long-range interaction. The central interest is on the dynamical evolution and final properties in that system. Results of study will be presented along with the discussion.
Trithos Rojjanason
24 October 2018
Title: Charged fermion in two-dimensional wormhole with constant magnetic flux
Abstract: We investigate the effects of magnetic field on the charged fermion in the two-dimensional wormhole. Applying external magnetic field along the axis direction of the wormhole, the Dirac equation is set up and analytically solved in the magnetic flux is constant along the throat of the wormhole. The system can be solved analytically and exact solutions are found, the quantized energy and eigenstates are obtained. The system exhibits both the spin-orbit coupling and the Landau quantization for the stationary states in both scenarios.
Asst. Prof. Dr. Sikarin Yoo-Kong
1 October 2018
Title: A vibrational structure for 1-form integrable hierarchies
Abstract: In this talk, we present a development on least action principle for Lagrangian 1-form structure both discrete-time and continuous-time cases. The Calogero-Moser system will be used as a toy model to show important features, i.e., duality between Lax compatibility and Lagrange closure relation and S^{1}-geometry of the space of independent variables. We will also mention a recent development on Feynman path integration for this Lagrangian 1-form structure.
ดร. วาสุเทพ หลวงทิพย์
26 September 2018
Title: Observations of accretion onto black holes at highest accretion rate
หลุมดําโดยธรรมชาติเป็นวัตถุอัดแน่น (compact object) ที่ไม่สามารถ สังเกตการณ์เข้าไปในขอบฟ้าเหตุการณ์ ได้ อย่างไรก็ตาม การศึกษาหลุมดําจากบริเวณรอบหลุมดําภายนอกขอบฟ้าเหตุการณ์ยังสามารถทําได้ โดยทั่วไป หลุมดําในทางดาราศาสตร์มักจะเกิดในระบบดาวคู่ (binary system) และอยู่ร่วมกันกับดาวคู่ของมัน (companion star) ในระบบดาวคู่หลุมดําที่เหมาะสม แก็สบางส่วนจากดาวคู่จะถูกดึงดูดเข้าหาหลุมดําเนื่องจากอิทธิพลของแรงโน้มถ่วงทําให้เกิดการรวมมวล (accretion) ขึ้นรอบๆภายนอกขอบฟ้าเหตุการณ์ของหลุมดํา นักดาราศาสตร์สามารถตรวจพบและศึกษาหลุมดําได้จากการศึกษาคลื่นแม่เหล็กไฟฟ้าที่เปล่งออกมาจากการรวมมวลเหล่านี้ ในสัมมนานี้ จะกล่าวถึงกระบวนการที่ทําให้การรวมมวลของหลุมดําเปล่งคลื่นแม่เหล็กไฟฟ้าออกมา โดยจะเน้นไปที่การศึกษาแหล่งกําเนิดรังสีเอกซ์แบบสว่างยิ่งยวด (ultraluminous X-ray source) ซึ่งเป็นวัตถุทางดาราศาสตร์ที่มีกําลังส่องสว่างสูงกว่า 1039 เอิร์กต่อวินาทีและถูกคาดว่าเป็นหลุมดําที่กําลังรวมมวลด้วยอัตราที่สูงที่สุด จากนั้นจะอภิปรายถึงกระบวนการทางฟิสิกส์ที่ทําให้แหล่งกําเนิดรังสีเอกซ์แบบสว่างยิ่งยวดมีกําลังส่องสว่างที่ระดับสูงมาก ท้ายที่สุดของการสัมมนา จะกล่าวถึงผลการศึกษาแหล่งกําเนิดรังสีเอกซ์แบบสว่างยิ่งยวด Holmberg IX X-1 ที่ถูกพบในดาราจักร Holmberg IX
Dr. Lunchakorn Tannukij
24 August 2018, 4PM
Title: Partially-massless theory as a quantum gravity candidate
Abstract: A partially-massless theory of gravity is a theory which propagates 4-degree-of-freedom graviton on a 4D de-Sitter space. Since the massive graviton in general has 5 degrees of freedom, this theory of "partially-massless" graviton has an extra gauge symmetry compared to that of massive graviton. In order to realize the partially-massless theory as a quantum theory, a matter coupling is introduced and it is found that to retain the gauge symmetry one must allow the matter field to transform nonlocally. Moreover, at the classical level one can find that, by choosing an appropriate time coordinate, both the tensor mode and the vector mode can propagate at a speed of light but not at the same time. Furthermore, quantization schemes for both modes are also suggested.
Asst. Prof. Dr. Patipan Uttayarat
22 August 2018, 2PM
Title: What do we know about dark matter-neutrino interaction?
Abstract: Dark matter (DM) and neutrino are the telltale signs of new physics beyond the Standard Model. Yet, very little is known about there properties and interactions. It's possible that DMs only interact with our sector via neutrinos, hence, making it difficult to probe. Fortunately, the advanced in technology provides us with various experimental tools to start probing the DM-neutrino interaction. In this talk, I will give the recent result on the DM-neutrino interaction.
Dr. Daris Samart
8 August 2018, 1PM
Title: Composite Nambu--Jona-Lasinio inflation near infrared fixed point of the Horava-Lifshitz theory
Abstract: In this work, we first propose a cosmological scenario inherently based on the effective Nambu--Jona-Lasio (NJL) model near the infrared (IR) limit of the Horava-Lifshitz (HL) theory. Having used the one-loop expansion correction, we employ the NJL framework in the ultraviolet (UV) limit of the HL theory, with critical exponent z=3, to demonstrate in the IR limit that the symmetry of the potential at the critical coupling value is broken at z=1. We also derive the effective Higgs-like potential in the low energy regimes. Here the symmetry of the effective potential will be broken near z=1 at a certain value of the critical coupling. In our scenario, the scalar channel of the NJL model plays the role of a composite inflaton. We find that the Lorentz invariance (LI) appears at the IR scale of the HL theory and employ the standard inflationary (slow-roll) machinery as a probe of physics at very high energy. We compute the inflationary parameters and compare them with recent Planck 2015 data. Interestingly, we discover that the predictions of the model are in perfect agreement with the Planck analysis. Our salient feature is that we used inflation to quantify the IR and UV fixed points of underlying theory. We interestingly discover that the IR fixed point of HL gravity is at the grand unified energy scale; whilst the UV fixed point is at the Planck energy scale.
Dr. Nick Poovuttikul
6 July 2018
Title: (Almost) conserved (higher form) currents in strongly interacting QFTs
Abstract: I will discuss an approach to understand low energy dynamics of strongly interacting quantum field theory from the point of view of conserved currents and global symmetries. These global symmetries can be explicitly broken and invalidate the conservation law. Nevertheless, there is a regime where the currents is still "almost conserved" and interplay with the other genuinely conserved currents in an interesting way. If time allows, I will also mentioned work in progress with Saso Grozdanov and Andy Lucas on how to extract some hidden almost conserved currents from various holographic models, their relation to the stretch horizon and how they affect the quasinormal mode spectrum of the black brane.