9 research outputs found
중력파를 이용한 암흑물질 물리학 탐사
Get PDF학위논문(박사) -- 서울대학교대학원 : 자연과학대학 물리학과, 2021.8. 최한길.In this dissertation, we present novel ways of probing dark matter(DM) physics through gravitational waves(GWs). We find that if a light scalar dark matter interacts with neutron and induces time-oscillating mass shift of it, GW chirps radiated by neutron star binary inspiral can be sensitive probe to such effects. The sensitivity comes from a large number of GW cycles during year-long measurements in broadband (0.01 Hz – 1000 Hz). Such broadband measurements that can be realized by a future detector network including LIGO and mid-band detectors will probe unconstrained parameter space of the light scalar DM.
We also show that gravitational lensing(GL) of GW can be a probe of dark matter subhalos at subgalactic scales(M < 10^7 solar mass). It has been very challenging for GL of light to probe the scale. What special to GW is its parsec scale Fresnel Length which comes from its long wavelength and cosmological distance to the GW source. It makes possible GW chirps to be diffracted by the parsec-scale subhalos. We show that the diffractive lensing signal is equivalent to a shear distribution of a lens object, and therefore, it can be used for reconstruction of the lens profile. The event rate of such GW lensing is estimated to O(10) per year at BBO.이 논문에서 우리는 중력파를 이용해 암흑물질 물리학을 탐사하는 새로운 방법을 보여준다. 우리는 가벼운 스칼라 암흑물질이 중성자와 상호작용해서 그것에 시간-진동성 질량 변화를 일으킨다면, 중성자별 쌍성의 나선운동에서 나온 중력파 처프 신호가 그 효과에 민감할 것임을 알아냈다. 그 민감함은 광대역(0.01 Hz – 1000 Hz)에서 1년 이상의 중력파 측정으로 얻은 매우 큰 수치의 중력파 진동횟수 덕분이다. 그러한 광대역 측정은 미래에 LIGO와 중간-주파수 중력파 관측기를 포함하는 관측소 네트워크에 의 해 실현될 수 있으며, 가벼운 스칼라 암흑물질의 아직 탐사되지 못한 파라메터 영역을 탐사할 것이다.
우리는 또한 중력파의 중력렌즈현상이 은하규모 미만(M < 10^7 태양질량)의 암흑물질 서브-헤일로 탐사할수 있는 수단임을 보였다. 빛의 중력렌즈현상으로는 그러한 규모를 탐사하기가 쉽지 않았다. 중력파의 특별한 점은 그것의 프레넬 길이가 파섹 규모라는 것인데, 이는 그것의 긴 파장과 파원까지의 우주론적 거리 덕분이다. 이는 중력파 처프 신호가 파섹 규모의 서브-헤일로에 의해 회절될 수 있게 했다. 우리는 그 회절성 렌즈 신호가 렌즈물체의 shear 분포와 동일함을 보였고, 따라서 그것이 렌즈의 물질분포를 재구성하는데 이용될 수 있음을 보였다. 그러한 중력파의 중력렌즈현상은 BBO 디텍터 에서 1년에 수십번 정도 관측할것으로 예측된다.1 Introduction 1
1.1 Gravitational waves in LinearizedGR 2
1.2 Gravitational wave radiation from a binary star 6
2 A New Probe of Dark Matter-Induced Fifth Force with Neutron Star Inspirals 11
2.1 Introduction 11
2.2 Overview 13
2.3 Models of DM-induced fifth force 15
2.4 Signals in Neutron Star inspirals 16
2.4.1 Oscillating NS-NS mass-shift 17
2.4.2 Other light-scalar (non-DM) effects in NS inspirals 18
2.4.3 Mass-shift in other experiments 19
2.4.4 Light-scalar(non-DM) effects in other experiments 21
2.4.5 Equivalence-principle violation 22
2.5 Broadband GW detectors and Calculation 22
2.6 Prospects 24
2.7 Discussion 27
2.7.1 Origin of good sensitivity 27
2.7.2 DM density dependence 30
2.8 Conclusion 30
3 Small-scale shear: peeling off diffuse subhalos with gravitational waves 33
3.1 Introduction 33
3.2 Diffractive lensing formalism 37
3.2.1 Lensing integral 37
3.2.2 Diffraction condition 39
3.2.3 Formalism for weak diffractive lensing 41
3.2.4 Shear as the origin of frequency dependence 44
3.2.5 Complete formalism with strong diffraction 46
3.3 NFW lensing 48
3.3.1 Profile 48
3.3.2 Critical curves 51
3.3.3 Diffractive lensing 52
3.4 GW detection of NFW 54
3.4.1 GW chirping 54
3.4.2 Log-likelihood detection 56
3.5 Prospects 59
3.5.1 Semi-analytic estimation 59
3.5.2 Results 62
3.6 Generalization 69
3.6.1 Lensing by power-law profiles 69
3.6.2 Semi-analytic estimation 72
3.6.3 Peeling off profiles 75
3.6.4 Core-vs-cusp 78
3.7 Summary 78
A Appendix for Diffractive lensing 80
A.1 MNFW scaling of milli-lensing perturbation 80
A.2 Range of diffractive lensing near a caustic 81
A.3 Single image of diffractive lensing 83
A.4 Formulation of lnp 84
A.5 Derivation of maximumlnp87
A.6 Example diffractive lensing cross-sections 88
Bibliography 90
초록 105
감사의 글 106박
(A) fast FMCW chirp synthesizer using harmonic compensation of VCO nonlinearity
No full text학위논문(석사) - 한국과학기술원 : 전기및전자공학부, 2020.8,[iv, 36 p. :]레이더 시스템을 구동하는 주파수 변조 연속파(FMCW) 합성기는 높은 선형성을 보장하면서 동시에 빠른 주파수 변조를 구현해야한다. 그러나 FMCW 주파수 합성기를 구성하는 위상고정루프는 저주파 통과 특성이 있어 빠른 주파수 변조를 구현하는 데 어려움이 있다. 투-포인트 모듈레이션 방법이 이러한 주파수 변조 연속파(FMCW) 주파수 합성기의 한계를 극복하기 위해 사용되고 있다. 하지만 전압제어발진기의 비선형성으로 인해 변조 오류가 생기는 문제가 있다. 본 논문에서는, 이러한 투-포인트 모듈레이션의 한계를 극복할 수 있는 새로운 구조를 제안하였다. 제안한 구조는 전압제어발진기의 비선형성을 고조파 보상하였다. 이를 통해 수 마이크로-초 수준의 빠른 주파수 변조를 구현하면서도 변조 오류를 최소화하였다.한국과학기술원 :전기및전자공학부
Effects of varying CO2, Nutrient and Light Irradiance Levels on the Growth of Ulva australis at Germling, Juvenile, and Adult Stages
No full textThe effects of CO2 concentration, nutrient levels, and irradiance on the growth of germlings and juveniles, and on the photosynthesis of adults were examined in a green tide alga, Ulva australis. We used a factorial experimental design with two CO2 concentrations (380 and 750 ppm), two nutrient levels (control and PES medium), and two irradiance levels (50 and 100μmol photons m−2s−1 ). Germlings grew best ( 664.15±61.45μm in length) under conditions of 750 ppm, PES, and 100μmol photons m−2s−1 after 10 days in culture. Relative growth rates (RGR) of the juveniles were greatest (4.41% day−1 ) under conditions of 750 ppm, PES, and 50μmol photons m−2s−1 after 5 days in culture. Photosynthetic efficiency ( Fv/Fm ) of the adult discs was 0.73±0.05 before the experiment and reached a maximum ( 0.83±0.01 ) under conditions of 750 ppm, control, and 50μmol photons m−2s−1 after 5 days in culture. Growth (germlings and juveniles) and photosynthesis (adult discs) of Ulva australis increased when CO2 levels were 750 ppm. Additionally, the optimal irradiance for growth and photosynthesis differed among stages, wherein germlings grew best at 100μmol photons m−2s−1 , juveniles grew best at 50μmol photons m−2s−1 , and adults photosynthesized most at 50μmol photons m−2s−1 . The performance of Ulva australis at all examined life stages was enhanced under the PES nutrient treatment. In conclusion, the physiological responses of U. australis to varying CO2 , nutrient, and irradiance levels differed slightly among life stages. However, growth and photosynthesis always increased with elevated CO2 and nutrient concentrations. These results indicate that U. australis green tide blooms might occur more frequently in coastal areas if CO2 and nutrient concentrations increase.22Nkc
Effects of varying CO2, Nutrient and Light Irradiance Levels on the Growth of Ulva australis at Germling, Juvenile, and Adult Stages
No full textThe effects of CO2 concentration, nutrient levels, and irradiance on the growth of germlings and juveniles, and on the photosynthesis of adults were examined in a green tide alga, Ulva australis. We used a factorial experimental design with two CO2 concentrations (380 and 750 ppm), two nutrient levels (control and PES medium), and two irradiance levels (50 and 100μmol photons m−2s−1 ). Germlings grew best ( 664.15±61.45μm in length) under conditions of 750 ppm, PES, and 100μmol photons m−2s−1 after 10 days in culture. Relative growth rates (RGR) of the juveniles were greatest (4.41% day−1 ) under conditions of 750 ppm, PES, and 50μmol photons m−2s−1 after 5 days in culture. Photosynthetic efficiency ( Fv/Fm ) of the adult discs was 0.73±0.05 before the experiment and reached a maximum ( 0.83±0.01 ) under conditions of 750 ppm, control, and 50μmol photons m−2s−1 after 5 days in culture. Growth (germlings and juveniles) and photosynthesis (adult discs) of Ulva australis increased when CO2 levels were 750 ppm. Additionally, the optimal irradiance for growth and photosynthesis differed among stages, wherein germlings grew best at 100μmol photons m−2s−1 , juveniles grew best at 50μmol photons m−2s−1 , and adults photosynthesized most at 50μmol photons m−2s−1 . The performance of Ulva australis at all examined life stages was enhanced under the PES nutrient treatment. In conclusion, the physiological responses of U. australis to varying CO2 , nutrient, and irradiance levels differed slightly among life stages. However, growth and photosynthesis always increased with elevated CO2 and nutrient concentrations. These results indicate that U. australis green tide blooms might occur more frequently in coastal areas if CO2 and nutrient concentrations increase.22Nkc
